question #3 Sahih al-Bukhari 3528, Book 61, Hadith 38 : What is the role of the Ansar in the context of this narration?

The Prophet (ﷺ) sent for the Ansar (and when they came), he asked, ‘Is there any stranger amongst you?”
They said, “No except the son of our sister.” Allah’s Messenger (ﷺ) said, “The son of the sister of some
people belongs to them.”