Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) says that Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) sought permission three times to come to Umar (may Allah be pleased with him), then went back. Umar (may Allah be pleased with him) asked: "Why did you not come to me?" He replied: "I heard the Prophet (peace and blessings be upon him) say: 'Whoever seeks permission should seek it three times; if he receives no answer, he should go back.'" Umar (may Allah be pleased with him) said: "Produce a witness for this, or I will punish you." Sayyiduna Abu Musa (may Allah be pleased with him) became alarmed and spoke to the people, and Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) said: "The youngest man among the people will bear witness for you." In those days I, Abu Sa'id, was the youngest among them, so I went and testified before Umar (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Whoever seeks permission three times and is not given permission should go back."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17664
Sayyiduna Kaladah bin al-Hanbal (may Allah be pleased with him) says that Sayyiduna Safwan bin Umayyah (may Allah be pleased with him) sent me to the Prophet (peace and blessings be upon him) with milk, a young deer and small cucumbers. I went in without saying the greeting of peace, so he (peace and blessings be upon him) sent me back and said: "Come back saying 'As-salamu alaykum' (Peace be upon you)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17665
Sayyiduna Kaladah bin al-Hanbal (may Allah be pleased with him) narrates that Safwan bin Umayyah sent him, at the time of the Conquest, with beestings (first milk), a young deer and small cucumbers, while the Prophet (peace and blessings be upon him) was in the upper part of the valley. He said: I went in to him without saying the greeting of peace and without seeking permission, so the Prophet (peace and blessings be upon him) said: "Go back and say: 'As-salamu alaykum (Peace be upon you), may I come in?'" This was after Safwan had accepted Islam.
Amr said: Umayyah bin Safwan also told me this report, but he did not say: I heard it from Kaladah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17666
It is reported from a man of Banu Amir that he said: I sought permission from the Prophet (peace and blessings be upon him): "May I enter?" He (peace and blessings be upon him) said to his servant: "Go and teach him how to seek permission, and tell him to say: 'As-salamu alaykum' (Peace be upon you), may I enter?" The man heard it, so he sought permission in the same way, and he was given permission.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17667
This has passed before.
(In this version the narrator said: I heard him say: "As-salamu alaykum (Peace be upon you), may I enter?") And it has been narrated to us from Ibn Abbas, from Umar (may Allah be pleased with them both), that he came to the Prophet (peace and blessings be upon him) while he was in an upper room of his, and said: "As-salamu alayka (Peace be upon you), O Messenger of Allah; as-salamu alayka, may Umar come in?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17669
Sayyiduna Jabir (may Allah be pleased with him) says: I came to the Prophet (peace and blessings be upon him) about a debt owed by my father and knocked on his door. He (peace and blessings be upon him) asked: "Who is it?" I said: "Me." He (peace and blessings be upon him) said: "Me, me," as though he (peace and blessings be upon him) disliked it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17670