When Ali (RAA) migrated to Medina he was 22 or 23 years old. Muhammad (SAW) selected Ali (RAA) to be his brother among his companions (sahaba).
For the ten years that Muhammad (SAW) led the community in Medina, Ali (RAA) was very active in his service as his secretary and deputy, serving in his militaries, the carrier of his flag in every battle, leading parties of soldieries on attacks, and transport messages and instructions. Ali (RAA) is one of Muhammad (SAW)'s lieutenants, and afterward his son-in-law, he was a person of power and sticking up in the Muslim community.