It is narrated about Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) that he sought permission three times to enter upon Sayyiduna Umar (may Allah be pleased with him), but was not granted permission. Sayyiduna Umar (may Allah be pleased with him) was perhaps busy at that time, so Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) returned. When Sayyiduna Umar (may Allah be pleased with him) became free, he inquired: "Did I not hear the voice of Abdullah bin Qais? Tell him to come in." Sayyiduna Umar (may Allah be pleased with him) was informed that he had already left. Sayyiduna Umar (may Allah be pleased with him) called for him (and inquired), so Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) explained, "We have been commanded regarding this matter." Sayyiduna Umar (may Allah be pleased with him) said: "Bring proof regarding this." So Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) went to the gathering of the Ansar and asked them about this matter. They said: "The one who is youngest among us will testify for you regarding this, and he is Abu Sa'id Khudri (may Allah be pleased with him)." So Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) took Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) with him, and he testified before Sayyiduna Umar (may Allah be pleased with him) regarding this matter (that it is so). Then Sayyiduna Umar (may Allah be pleased with him) said: "This command of the Noble Prophet (peace and blessings of Allah be upon him) remained hidden from me; buying and selling in the market kept me unaware of it. However, accept whatever you wish (or greet as you wish)."