Bond of Brotherhood
After the migration to Medina, the Holy Prophet (sa) established a bond of brotherhood between Hazrat Mus‘ab (ra) bin Umair and Hazrat Abu Ayyub Ansari (ra).
(al-Tabaqaat-ul-Kubra li ibn Sa‘d, Vol. 3, p. 88, Mus‘ab (ra) bin Umair, Dar-ul-Kutub al-Ilmiyyah, Beirut, 1990)