The Prophet ﷺ stood up that day to deliver a sermon. He praised Allah and extolled Him, then sought forgiveness for the martyrs who had been killed at the Battle of Uhud. Then he said, "Company of Emigrants, your numbers continue to grow, while the Ansar will not increase. The Ansar are my trusted confidants to whom I have turned for refuge. Honor those among them who are noble, and overlook the faults of those who err among them, for they have fulfilled their duty, and what remains is owed to them."
أن النبي ﷺ قام يومئذ خطيبا، فحمد الله وأثنى عليه، واستغفر للشهداء الذين قتلوا يوم أحد، ثم قال: إنكم يا معشر المهاجرين تزيدون، وإن الأنصار لا يزيدون، وإن الأنصار عيبتي التي أويت إليها، أكرموا كريمهم، وتجاوزوا عن مسيئهم، فإنهم قد قضوا الذي عليهم، وبقي الذي لهم.
Ahmad (21951) narrated it from Abdul-Razzaq, and it is also in his Musannaf (19917), from Maamar, who said, Zuhri said, "Abdul-Rahman bin Kaab bin Malik informed me, whose father was one of the three whose repentance was accepted, from a man among the companions of the Prophet ﷺ, that he said," and then he related it. Its chain is sahih. Haythami said, "Its narrators are the narrators of the Sahih."A note of caution, in Abdul-Razzaq's chain it appears as "Abdullah bin Abdul-Rahman bin Kaab bin Malik, from his father." And in the printed edition of Tabarani, the mention of "a man among the companions of the Prophet ﷺ" has dropped out.Ahmad also narrated it in his Musnad (16075), and in Fadail (1412), from Abu Yaman, who said, Shuayb informed us, from Zuhri, who said, "Abdullah bin Kaab bin Malik Ansari informed me, that is, his father was one of the three whose repentance was accepted, that some of the companions of the Prophet ﷺ informed him," and he said, and then he related it.His saying, "The Ansar are my treasure chest," means my special people and the place where I keep my secrets. The Arabs figuratively call hearts and chests "chests" (ayab) because they are the repositories of secrets. Nihayah (3/272).