Sayyiduna al-Bara' (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) sent some men of the Ansar to Abu Rafi' and appointed Sayyiduna Abdullah (may Allah be pleased with him) as their commander. He mentioned the hadith in the same way, except that he said: I went along and stayed close to the gatekeeper; then I went in and hid. When the people had entered, he closed the gate and hung the keys on a peg.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18101