Musnad Ahmad Hadith 19581

It is narrated from Ubaid bin Umair (may Allah have mercy on him) that once Abu Musa Ash'ari (may Allah be pleased with him) greeted Umar (may Allah be pleased with him) three times, but did not receive permission, so he left. After a short while, Umar (may Allah be pleased with him) said, "Did I not just hear the voice of Abdullah bin Qais?" The people said, "Yes." Umar (may Allah be pleased with him) sent a messenger after him asking, "Why did you leave?" He replied, "I sought permission three times, and when I was not granted permission, I left. This is what we have been commanded to do." Umar (may Allah be pleased with him) said, "Present a witness for this, otherwise I will punish you." Abu Musa (may Allah be pleased with him) went to a gathering of the Ansar. They said, "Even the youngest among us can testify to this." So Abu Saeed Khudri (may Allah be pleased with him) went with him and testified to it. Then Umar (may Allah be pleased with him) said, "This command of the Noble Prophet (ﷺ) was hidden from me; the affairs of the markets kept me heedless of it."