With the move to Medina, the Prophet encountered a challenge – how to  bring about harmony and introduce two distinct groups to one another –  the Muhajiroon, those who had converted in Mecca and had to leave their  home to move to Yathrib and the Ansar, those who had converted in the  city of Yathrib and were now in a position to have to welcome in  hundreds of people into their city. What would Prophet Muḥammad do to  bring these people together and WHO did he choose as his brother?