Sayyiduna Abu Bakr was two years junior to the Prophet ﷺ and had been his closest friend and companion since before the Revelation. He was a wealthy merchant from the Taym clan of Quraysh. When he embraced Islam, he spent most of his money on charity and freeing Muslim slaves who were being persecuted. Abu Bakr's faith in Islam was so strong that the Prophet ﷺ later said that everyone had paused and taken time to think when invited to Islam, except for Abu Bakr, who had immediately accepted the faith.
When the Prophet went on the Night Journey to Jerusalem, he told his followers about it the following day. The unbelievers of Makkah found out about it, and they were full of mockery, challenging the Muslims, saying,
Do you seriously believe your so-called prophet travelled all the way to Jerusalem and back in a single night? A journey that takes weeks?
Some of the Muslims actually began to waver in their faith, it seemed so hard to fathom. However, when the Unbelievers came to Abu Bakr to challenge him about this, he immediately replied that he totally believed it without doubt. This is why he was given the title, al-Siddiq (The Truthful).
The death of the Prophet ﷺ was a great shock for many companions. Umar, another leading companion of the prophet, stood in the masjid with a drawn sword and shouted out that the prophet had not died but had gone to visit his Lord and would return, like Moses had done.
The Muslims fell into confusion, until Abu Bakr arrived on the scene. He went into the house of Aisha where the prophet lay, kissed his forehead, and said,
Let my father and mother be sacrificed for you. By Allah, Allah will never cause you to die twice. As for the death which was written for you, it has come upon you.
Abu Bakr went into the masjid, and the Muslims gathered around him. He said:
Whoever of you worshipped Muhammad, let him know that Muhammad is dead. And whoever worshipped God, let him know that God is Alive and never dies.
He then recited from the Quran:
And Muhammad is but a messenger; messengers have passed before him; if then he dies or is killed will you turn back upon your heels?...
When Umar heard the words of Abu Bakr, his legs gave way beneath him, and he collapsed, realizing that the prophet ﷺ had indeed passed away. God had strengthened Abu Bakr in this time of intense shock for the Muslims, and Abu Bakr was able to reassure them and keep them strong in the faith.
As preparations for the Holy Burial were taking place, news reached the muhajirun (immigrants from Makkah) that the ansar (Muslims of Medina) had gathered to appoint a successor to lead the Muslim ummah (Islamic community). Upon realising the urgency of the situation, several leading Muhajirun headed for the meeting.
Some of the Ansar felt that the new leader should come from their people, as they were the majority in Medina, but Abu Bakr reminded them that the Arab tribes would never accept a leader who was not from Quraysh. Abu Bakr recommended Umar or Abu Ubayda for the role.
The discussions became heated, voices were raised, and a clamour arose. Umar, recognizing the delicacy of the situation, urged Abu Bakr to stretch out his hand and swore allegiance to him. Seeing this action of the two foremost Companions, others quickly followed suit, and Abu Bakr was declared the first Caliph of Islam by consensus.
Before the Prophet died, he had dispatched an army, led by Usama ibn Zayd, against the Romans to the north. The army had proceeded a short distance from Medina and Abu Bakr's advisors, the senior Companions, urged him to call it back, especially as rumours were beginning to reach Medina that some of the Arab tribes were throwing off their allegiance to Islam and turning against the Muslims. The Companions advised that the army would be needed to deal with the urgent situation closer to home. However, Abu Bakr refused to recall the army, stating "By Allah, that I be plucked away by birds is preferable to me than to begin by reversing an order of the Messenger of God!"
Abu Bakr was a man of unwavering faith who was committed to striving in the Path of God. He faced several challenges during his two-year reign, including tribes reneging on their allegiance to Islam (apostates) and false prophets rising up in the corners of the Arabian Peninsula. Some tribes proclaimed that they remained Muslim but they would no longer send their zakat to Medina as they had during the lifetime of the Prophet ﷺ. Abu Bakr insisted on the tribes paying zakat and declared that he would fight anyone who differentiated between the obligations of prayer and zakat.
Abu Bakr arranged the Muslim forces into eleven separate armies, each with a commander and a standard, and sent them against the rebelling tribes ('the Wars of Apostasy'). Battle after battle, although severely outnumbered, the Muslim forces were victorious, and the whole of Arabia was gradually brought back under the authority of the Caliph in Medina.
One of the fiercest battles was against the false prophet known as Musaylima the Liar. He led the legions of the Banu Hanifa tribe against Medina but was defeated by an army led by Khalid ibn Waleed. Many huffaz (those who memorised the entire Quran) were martyred in this battle, and this prompted Abu Bakr, on the suggestion of Umar, to issue instructions for the Quran to be collected together as a written copy for the first time. This was duly completed by Zayd ibn Thabit, constituting one of the many legacies and services of Abu Bakr for Islam.
Abu Bakr was blessed as being the one who accompanied the Prophet Muhammad ﷺ during the Hijra (emigration to Yathrib). At one point, he and the Prophet were hiding in a cave and the enemies almost found them, but they were saved by a miracle from God. The Quran refers to this event:
...still Allah helped him when those who disbelieve drove him forth, the second of two; when they two were in the cave, when he said unto his comrade: Grieve not. Lo! Allah is with us ...
[Quran 9:40]