Who is Mu'adh ibn Jabal?

Mu'adh ibn Jabal was an illustrious Companion who witnessed al-Aqabah, Badr, and all the battles with the Prophet, peace and blessings be upon him. He compiled the Qur'an during the Prophet's lifetime and was one of the four from whom the Prophet commanded the taking of the Qur'an. He was renowned for his knowledge of lawful and unlawful matters, and the Prophet said of him: "And the most knowledgeable among them concerning lawful and unlawful matters is Mu'adh." The Prophet, peace and blessings be upon him, appointed him as his deputy in Mecca to teach the people, and sent him to Yemen as a caller to Islam and a teacher. He passed away during the Plague of Amwas in the seventeenth or eighteenth year of the Hijra.