Ubayy ibn Ka'b (Arabic: أُبَيّ ٱبْن كَعْب, ʾUbayy ibn Kaʿb) (died 649), also known as Abu Mundhir,[1][2] was a companion of the Islamic prophet Muhammad and a person of high esteem in the early Muslim community.
[2] He was one of the first to accept Islam and pledge allegiance to Muhammad at al-Aqabah before the migration to Medina, becoming one of the Ansar.
[3] Following Muhammad's death, he was one of the twenty-five Hafiz, people who knew the Qur'an completely by heart.
[citation needed] He was part of the consultative group (mushawarah) to which the caliph Abu Bakr referred many problems.
[citation needed] Ubayy died in the year 649 AD (30 AH), during the caliphate of Uthman.