Tirmidhi

Explanation:
1:
This statement is intended to reassure the Ansar,
meaning, for the sake of pleasing the Ansar, I could go so far that if it were possible, I would have become one of the Ansar myself.
However, changing lineage is not possible; this is an acknowledgment of the Ansar’s devotion and sacrifice for Islam.
The next statement, however, is possible: “If the Ansar were to walk in a valley, I would walk with them.” If such a situation were to arise, since the mutual love between the Muhajirun and the Ansar was for the sake of Allah and His Messenger (sallallahu alayhi wa sallam), such a situation never actually arose between them.
Radi Allahu anhum ajma‘in.