It is narrated from Hazrat Anas (may Allah be pleased with him) that during the blessed era of the Prophet (peace and blessings be upon him), four companions (may Allah be pleased with them) had memorized the entire Qur'an, and all four belonged to the Ansar: Hazrat Ubayy bin Ka'b (may Allah be pleased with him), Hazrat Mu'adh bin Jabal (may Allah be pleased with him), Hazrat Zayd bin Thabit (may Allah be pleased with him), and Hazrat Abu Zayd (may Allah be pleased with him).