The passing of Bahá’u'lláh on 28 May 1892 in the Mansion of Bahji marks the beginning of the most turbulent epoch within the Bahá’í community, an epoch which witnessed the onslaught of the unfaithful against the Cause on a far greater scale than any so far encountered in the course of its eventful history… The blessed remains of Bahá’u'lláh were not yet laid to rest when Mirza Muhammad-’Ali revealed his true self. Up till then he had given the appearance of being loyal to his Father and to ‘Abdu’l-Bahá, but now he launched his ignoble plans to undermine the foundation of the Covenant and overthrow ‘Abdu’l-Bahá, its Centre.
Adib Taherzadeh, The Covenant of Bahá’u’lláh, p. 147

Who was Mizra Muhammad-Ali?

[The] arch-breaker of the Covenant of Bahá’u'lláh is Mirza Muhammad-’Ali, the eldest son of Bahá’u'lláh’s second wife Mahd-i-’Ulya. He was born in Baghdad in the first year of Bahá’u'lláh’s arrival there. From the early days of his youth, he found that he could not rise to the level of ‘Abdu’l-Bahá, who was nine years his senior. He lacked those spiritual qualities which distinguished his eldest brother, who became known as the Master from the early days in Baghdad.

The most essential prerequisites for the spiritual survival of all those who were close to Bahá’u'lláh were humility, self-effacement and utter nothingness in His presence. If these qualities were missing in an individual, he would be in great danger of spiritual downfall and eventual extinction.

While ‘Abdu’l-Bahá, the Greatest Holy Leaf, the Purest Branch, and their illustrious mother were all embodiments of servitude and selflessness, Muhammad-’Ali, his brothers and sister, together with their mother, were the opposite. Although the latter group were all sheltered beneath Bahá’u'lláh’s protection, and flourished through the outpouring of His favours, in reality they were the victims of selfish desires and worldly ambitions. During Bahá’u'lláh’s lifetime they were subdued by His authority and kept under control through His admonitions. At the same time, Mirza Muhammad-’Ali and his brothers were the recipients of a great many favours from the believers who, because of their love for Bahá’u'lláh, honoured and revered them too. Thus these three sons acquired an undeserved prestige and basked in the sunshine of their Father’s glory and majesty.

Inwardly, Mirza Muhammad-’Ali was a faithless person, and he led his two younger brothers in the same direction. But outwardly he utilized the power of the Faith and the resources of the community to bolster up his own image in the eyes of the followers of Bahá’u'lláh. He emerged as an important person in the service of his Father by transcribing some of His Tablets and by the use of calligraphy of which he was a master. From the days of his youth he entertained the ambition to occupy a position of eminence within the Faith, a position similar to that of ‘Abdu’l-Bahá, who, from early on, had distinguished Himself among the entire family.

In Muhammad-’Ali’s childhood Bahá’u'lláh conferred upon him the power of utterance, and this became obvious as he grew up. But instead of utilizing this gift to promote the Cause of God, he embarked on a career which hastened his downfall. When he was in his early teens in Adrianople, he composed a series of passages in Arabic and without Bahá’u'lláh’s permission disseminated them among some of the Persian Bahá’ís, introducing them as verses of God which, he claimed, were revealed to him. He intimated to the believers that he was a partner with Bahá’u'lláh in divine Revelation. Several believers in Qazvin were influenced by him and drawn to him.

…In his writings, which are of considerable length, the teen-age Muhammad-’Ali refers to himself, among other things, as ‘the King of the spirit’, calls on the believers to ‘hear the voice of him who has been manifested to man’, admonishes those who deny his verses revealed in his childhood, declares his revelation to be ‘the greatest of God’s revelations’, asserts that ‘all have been created through a word from him’, considers himself to be ‘the greatest divine luminary before whose radiance all other suns pale into insignificance’, and proclaims himself to be ‘the sovereign ruler of all who are in heaven and on earth’.

Such preposterous claims, such a display of personal ambition, evoked the wrath of Bahá’u'lláh, who rebuked him vehemently and chastised him with His own hands.”
Adib Taherzadeh, The Covenant of Bahá’u’lláh, p. 125

What did Mirza Muhammad-Ali do after the passing of Bahá’u’lláh?

Far from being allayed by the provisions of a Will which had elevated him to the second-highest position within the ranks of the faithful, the fire of unquenchable animosity that glowed in the breast of Mirza Muhammad-’Ali burned even more fiercely as soon as he came to realize the full implications of that Document. All that ‘Abdu’l-Bahá could do, during a period of four distressful years, His incessant exhortations, His earnest pleadings, the favors and kindnesses He showered upon him, the admonitions and warnings He uttered, even His voluntary withdrawal in the hope of averting the threatening storm, proved to be of no avail. Gradually and with unyielding persistence, through lies, half-truths, calumnies and gross exaggerations, this “Prime Mover of sedition” succeeded in ranging on his side almost the entire family of Bahá’u'lláh, as well as a considerable number of those who had formed his immediate entourage. …Even Mirza Aqa Jan, who for forty years had labored as Bahá’u'lláh’s amanuensis, as well as Muhammad-Javad-i-Qasvini, who ever since the days of Adrianople, had been engaged in transcribing the innumerable Tablets revealed by the Supreme Pen, together with his entire family, threw in their lot with the Covenant-breakers, and allowed themselves to be ensnared by their machinations.

Forsaken, betrayed, assaulted by almost the entire body of His relatives, now congregated in the Mansion and the neighboring houses clustering around the most Holy Tomb, ‘Abdu’l-Bahá, already bereft of both His mother and His sons, and without any support at all save that of an unmarried sister, His four unmarried daughters, His wife and His uncle (a half-brother of Bahá’u'lláh), was left alone to bear, in the face of a multitude of enemies arrayed against Him from within and from without, the full brunt of the terrific responsibilities which His exalted office had laid upon Him.”
Shoghi Effendi, God Passes By, p. 245

In a celebrated Tablet, the Lawh-i-Hizar Bayti (Tablet of One Thousand Verses) ‘Abdu’l-Bahá describes the grievous events which occurred immediately before and just after the ascension of Bahá’u'lláh. He states that during the days of Bahá’u'lláh’s illness, He, ‘Abdu’l-Bahá, was in attendance on His blessed Person by day and by night, most of the time in a state of deep sorrow and depression. One day as He lay in His sick-bed, Bahá’u'lláh ordered ‘Abdu’l-Bahá to gather all those of His papers which were in the room and place them in two special cases. It was Bahá’u'lláh’s practice that whenever He left the Mansion for ‘Akká or elsewhere, He used to put all His papers in these large cases. Aware of the implications of this command, ‘Abdu’l-Bahá was shaken to the very depths of His being. As He hesitated to comply, Bahá’u'lláh reiterated His orders. With trembling hands and tearful eyes, ‘Abdu’l-Bahá was beginning to gather the papers when Majdu’d-Din entered the room.

…In this Tablet, ‘Abdu’l-Bahá further describes the agony of His heart as He forced Himself to gather Bahá’u'lláh’s papers. Seeing  Majdu’d-Din, ‘Abdu’l-Bahá asked for his assistance, so that this task, so extremely painful to Him, might be soon finished. When all the papers, the seals and other items had been locked into the cases, Bahá’u'lláh said to ‘Abdu’l-Bahá, ‘These two now belong to you.’ These words, implying the approach of the final hours of Bahá’u'lláh’s earthly life, pierced ‘Abdu’l-Bahá’s heart like an arrow.

When the ascension took place, ‘Abdu’l-Bahá’s grief knew no bounds. The shock He sustained as a result of this calamitous event was so intense that He found it difficult to describe it. He says that in the morning, along with His brother, He began the task of preparing the remains for burial. When they were about to wash Bahá’u'lláh’s blessed body, Mirza Muhammad-’Ali suggested to ‘Abdu’l-Bahá that since the floor would become wet, it would be better to take the two cases out of the room into Badi’u'llah’s room. ‘Abdu’l-Bahá was at that point in such a state of shock and grief that He was almost unconscious of His surroundings. He never thought that behind this suggestion could be a treacherous plot designed to rob Him of that precious trust.

He agreed, and the two cases were taken out and that was the last He saw of them.

The sacred remains were laid to rest that same day. ‘Abdu’l-Bahá was disconsolate and heartbroken. He says that for three consecutive days and nights He could not rest a single moment. He wept for hours and was in a state of unbearable grief. The Light of the World had disappeared from His sight and all around Him had been plunged into darkness. On the fourth night after the ascension, He arose from His bed around midnight and walked a few steps hoping that it might help to bring a measure of tranquillity to His agonized heart. As He began to pace the room, He saw through the window a scene His eyes could scarcely believe. His unfaithful brothers had opened the cases and were looking through Bahá’u'lláh’s papers, those papers which had been entrusted to Him!

‘Abdu’l-Bahá was deeply disturbed by the treachery of His brothers so soon after the ascension of their Father. This act of unfaithfulness committed so dishonourably against the most sacred trust of God, inflicted further pain and suffering upon His sorrow-laden heart. He returned to His bed immediately after this incident, for He did not wish His brothers to know He had seen them interfering with the contents of the cases. At this point ‘Abdu’l-Bahá thought to Himself that since His brothers had not seen the Will and Testament of Bahá’u'lláh, which was in ‘Abdu’l-Bahá’s possession, they were trying to find some document among His Writings with which to justify their intended action of undermining the foundation of the Cause of God and creating a division within the ranks of its avowed supporters. However, ‘Abdu’l-Bahá hoped, when they saw the Will and Testament, their efforts would be frustrated and they would then return His trust to Him.

But alas, this did not happen! The Kitáb-i-’Ahd was read by Aqa Riday-i-Qannad on the ninth day after the ascension of Bahá’u'lláh in the presence of nine witnesses chosen from among Bahá’u'lláh’s companions and members of Bahá’u'lláh’s family, including Mirza Muhammad-’Ali. On the afternoon of the same day it was read by Majdu’d-Din in the Shrine of Bahá’u'lláh before a large company of the friends, consisting of the Aghsan, the Afnan, the pilgrims and resident believers. ‘Abdu’l-Bahá says that after the Kitáb-i-’Ahd was read and its contents noted, some rejoiced with exceeding gladness and some grieved with great sorrow. The faces of the faithful were illumined with the light of joy, and those of the falsehearted were covered in the dust of despondency and gloom. ‘Abdu’l-Bahá states that on that day the foundations of Covenant-breaking were laid, the ocean of vain imagining began to surge, and the fire of dissension and strife was lit, its flame burning more fiercely with the passage of time and consuming the hearts and souls of the faithful in its tormenting heat.

Soon after that historic day when the Kitáb-i-’Ahd was read, one of the Afnan asked ‘Abdu’l-Bahá to use one of Bahá’u'lláh’s blessed seals to seal a Tablet which had been revealed by Bahá’u'lláh in his honour. When ‘Abdu’l-Bahá asked His brothers to give Him the seals of Bahá’u'lláh which had been placed in the cases, they pleaded ignorance, saying they did not know anything about the two cases! Bewildered and perplexed by such a remark, ‘Abdu’l-Bahá was plunged further into sorrow and grief. He describes how His whole being began to tremble when He heard such a response from His brothers, and knew that great tests and trials lay ahead.

Indeed the Kitáb-i-’Ahd had the same effect on the believers as an examination paper does on the pupils: divided into two categories, those who pass and those who fail. As soon as the contents of the Kitáb-i-’Ahd were made public the community was divided into two. Those who remained faithful to its sacred provisions rose to exalted realms of certitude and entered the ark of salvation. Those who violated the provisions were spiritually cast out of the community and returned to the deadly abodes of their own self and passions.

Although the violation of the Covenant of Bahá’u'lláh began in earnest immediately after His ascension, ‘Abdu’l-Bahá did not disclose the rebellion of Mirza Muhammad-’Ali, and a host of others who followed him in the Holy Land, to the believers in the East or the West. He tried, as He put it, to stop the foul odour of Covenant-breaking from spreading. He endured in silence for about four years all the suffering and humiliation that they heaped upon Him, as well as their onslaught against the Cause of which He was the only Centre. During these years He endeavoured to His utmost to guide these wayward people, who were intent upon destroying the Edifice of the Cause of God, to the path of truth and to infuse into their dying souls the breath of life. But they were haughty and vainglorious, and His loving counsels and admonitions did not penetrate the hardness of their hearts. At the end it was they themselves who disseminated their evil suggestions and vain imaginings among the believers.

The whole story of the violation of the Covenant by Mirza Muhammad-’Ali was initially made public by himself. Soon the disease spread through Persia and later in the West, and the plague of Covenant-breaking encompassed the community of the Most Great Name everywhere. Consequently ‘Abdu’l-Bahá wrote innumerable Tablets in which He told the story of Covenant-breaking, unmasked the ugly face of this misguided rebellion, named the violators of the Covenant, demonstrated their unfaithfulness and their evil designs and expatiated on His own sufferings at their hands. He elucidated in great detail the basic principles of the Covenant, its origins, its power and its indestructibility. He also urged the believers to remain steadfast in the Covenant, and inspired them to scale loftier heights in service to His Cause.

Adib Taherzadeh, The Child of the Covenant, p.149-151

Mirza Muhammad-’Ali tried different means by which to bring about ‘Abdu’l-Bahá’s death. One of his men, on two different occasions, placed poison in a jug of His drinking water. This was discovered in time. On another occasion one of the Covenant-breakers carried a dagger hidden under his clothes with the intention of taking ‘Abdu’l-Bahá’s life but he did not succeed in his attempt. Later both men regretted their actions. ‘Abdu’l-Bahá forgave one and turned a blind eye to the other. These two later left the Holy Land and went to Tihran.

Before incarceration was imposed on Him, ‘Abdu’l-Bahá used to frequent the city of Haifa to supervise the building work on the Shrine of the Báb. He used to meet the believers in the evenings and often late in the night He would proceed to His residence. Always, against His wishes, some believer concerned for His protection would walk a few yards behind Him. Late one night a gunman hired by Mirza Muhammad-’Ali fired three shots at the Master, all of which failed to hit Him. The believer who was walking behind rushed forward and the gunman ran away. ‘Abdu’l-Bahá did not show the slightest sign of perturbation at this incident and kept on walking, as always, with great dignity and majesty.
Adib Taherzadeh, The Child of the Covenant, p. 206