Abu Bakr Abdallah ibn Uthman Abi Quhafa (Arabic: , romanized: Ab Bakr Abd Allh ibn Uthmn Ab Quhfa; c.573 23 August 634) was the senior companion and was, through his daughter Aisha, a father-in-law of the Islamic prophet Muhammad, as well as the first caliph of Islam. He is known with the honorific title al-Siddiq by Muslims.

Abu Bakr became one of the first converts to Islam and extensively contributed his wealth in support of Muhammad's work. He was among Muhammad's closest companions, accompanying him on his migration to Medina and being present at a number of his military conflicts, such as the battles of Badr and Uhud.

Following Muhammad's death in 632, Abu Bakr succeeded the leadership of the Muslim community as the first Rashidun Caliph. During his reign, he overcame a number of uprisings, collectively known as the Ridda Wars, as a result of which he was able to consolidate and expand the rule of the Muslim state over the entire Arabian Peninsula. He also commanded the initial incursions into the neighbouring Sassanian and Byzantine empires, which in the years following his death, would eventually result in the Muslim conquests of Persia and the Levant. Abu Bakr died of illness after a reign of 2 years, 2 months and 14 days, the only Rashidun caliph to die of natural causes.

Muhammad ibn Abdullah (Arabic: مُحَمَّد ٱبن عَبْد ٱللَّٰه, romanized: Muḥammad ibn ʿAbd Allāh Classical Arabic pronunciation: [muˈħammad]; c. 570 – 8 June 632 CE) was an Arab religious, social, and political leader and the founder of the world religion of Islam. According to Islamic doctrine, he was a prophet, divinely inspired to preach and confirm the monotheistic teachings of Adam, Abraham, Moses, Jesus, and other prophets. He is believed to be the final prophet of God in all the main branches of Islam, though the modern Ahmadiyya movement diverges from this belief. Muhammad united Arabia into a single Muslim polity, with the Quran as well as his teachings and practices forming the basis of Islamic religious belief.

Muhammad was born approximately 570 CE in Mecca. He was the son of Abdullah ibn Abd al-Muttalib and Amina bint Wahb. His father Abdullah was the son of Quraysh tribal leader Abd al-Muttalib ibn Hashim, and he died a few months before Muhammad's birth. His mother Amina died when he was six, leaving Muhammad an orphan. He was raised under the care of his grandfather, Abd al-Muttalib, and paternal uncle, Abu Talib. In later years, he would periodically seclude himself in a mountain cave named Hira for several nights of prayer. When he was 40, Muhammad reported being visited by Gabriel in the cave and receiving his first revelation from God. In 613, Muhammad started preaching these revelations publicly, proclaiming that "God is One", that complete "submission" (islām) to God is the right way of life (dīn), and that he was a prophet and messenger of God, similar to the other prophets in Islam.Muhammad's followers were initially few in number, and experienced hostility from Meccan polytheists for 13 years. To escape ongoing persecution, he sent some of his followers to Abyssinia in 615, before he and his followers migrated from Mecca to Medina (then known as Yathrib) later in 622. This event, the Hijra, marks the beginning of the Islamic calendar, also known as the Hijri Calendar. In Medina, Muhammad united the tribes under the Constitution of Medina. In December 629, after eight years of intermittent fighting with Meccan tribes, Muhammad gathered an army of 10,000 Muslim converts and marched on the city of Mecca. The conquest went largely uncontested and Muhammad seized the city with little bloodshed. In 632, a few months after returning from the Farewell Pilgrimage, he fell ill and died. By the time of his death, most of the Arabian Peninsula had converted to Islam.The revelations (each known as Ayah – literally, "Sign [of God]") that Muhammad reported receiving until his death form the verses of the Quran, regarded by Muslims as the verbatim "Word of God" on which the religion is based. Besides the Quran, Muhammad's teachings and practices (sunnah), found in the Hadith and sira (biography) literature, are also upheld and used as sources of Islamic law (see Sharia).