It is narrated from Muhammad bin Umar (al-Waqidi) that the Messenger of Allah (peace and blessings be upon him) established brotherhood between Sayyiduna Abu Ayyub al-Ansari and Sayyiduna Mus'ab bin Umayr (may Allah be pleased with them both). Sayyiduna Abu Ayyub (may Allah be pleased with him) took part in the Battles of Badr, Uhud and al-Khandaq, and in all the campaigns alongside the Messenger of Allah (peace and blessings be upon him). He passed away during the caliphate of Sayyiduna Mu'awiyah (may Allah be pleased with him), in the year 52 AH, at the time when Yazid bin Mu'awiyah campaigned against Constantinople. His grave is at the foot of the fortress of Constantinople in the land of the Romans. It is mentioned regarding it that people visit it frequently, repair it, and when drought strikes, they pray for rain (from Allah) through it.