[1] The companions played a major role in Muslim battles, society, hadith narration, and governance during and after the life of Muhammad.

However, there were clearly many others who had some contact with Muhammad, and many of those names and biographies were recorded in religious reference texts such as ibn Sa'd's early Book of the Major Classes.

According to an observation in al-Qastallani's Al-Muwahib al-Ladunniyyah, an untold number of persons had already converted to Islam by the time Muhammad died.

The Sunni scholar ibn Hajar al-Asqalani (d. 852 H) said, The most correct of what I have come across is that a Sahâbî (Companion) is one who met the Prophet Muhammad, peace be upon him, whilst believing in him, and died as a Muslim.

According to Sunni scholars, Muslims of the past should be considered companions if they had any contact with Muhammad, and they were not liars or opposed to him and his teachings.

[12] The Shia[13][14] as well as some Sunni scholars like Javed Ahmad Ghamidi and Amin Ahsan Islahi follow a stricter definition, believing that not every Muslim who met Muhammad should be considered a companion.

In their view, the Qurʻan requires companions to demonstrate a high level of faith; thus, only those individuals who had substantial contact with Muhammad should be considered, e.g., those that lived with him, took part in military campaigns, or proselytized.

Then Abd al-Rahman ibn Awf and Uthman, companion and son-in-law of Muhammad and also essential chief of the Banu Umayyah, selected Umar as the second caliph after the death of Abu Bakr and the other Anṣār and Muhajirun accepted him.

The Shia claim that Muhammad announced his successor during his lifetime at Da'wat Dhu al-Ashira,[20] then many times during his prophethood and finally at the event of Ghadir Khumm.

[21] Shias consider that any hadith where Muhammad is claimed to have absolved all ṣaḥābah from sin is a false report by those who opposed the Ahl al-Bayt.