After Abu Bakr Siddiq (raa) emancipated Bilal (raa) from Umaiya Bin Khalaf, he appointed Bilal (raa) as his own store-keeper and later he came to serve to the Messenger of Allah (saws). When the Holy Prophet (saws) granted permission to his companions to migrate, Bilal (raa), along with the other companions of the Holy Prophet (saws), migrated to Yathrib, which would eventually be known as Medina, which in Arabic means "City".
Once in Medina, Bilal (raa) struggled when ever he was separated from the Messanger of Allah (saws) even though he had lived in the same house with the Prophets (saws) Khalil (intimate friend), Abu Bakr Siddiq and Aamir bin-Fahria (raa).
Due to his personal struggle of seperation, just as he did in Mecca, Bilal ibn Rabah (raa) would always accompany the Prophet (saws) on all the journeys he undertook as well as being involved in all the battles that look place during the Prophets (saws) lifetime.
The Hijra to Medina also brought on a new level of unity between the Muslims, the Messenger of Allah (saws) established the bond of brotherhood between the Muhajireen (Migrants) and Ansar (Helpers, Supporters). It was also at this time that Bilal (raa) a Muhajireen and Abu Rouwaiha, one of the Ansar (raa), became brothers unto each other.