Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: Sayyiduna Abdullah bin Qays (may Allah be pleased with him) greeted Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) with salam three times, but he did not give him permission, so he went back. Sayyiduna Umar (may Allah be pleased with him) sent a man after him, and when he came, he asked: Why did you do this? He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "When one of you greets three times and receives no reply, let him go back." Sayyiduna Umar (may Allah be pleased with him) said: Bring me proof of this, or else I will do such-and-such to you. Sayyiduna Abu Musa (may Allah be pleased with him) came, and his colour had changed. I too was present in that circle. We asked: What is the matter? He said: I greeted Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) with salam and he said such-and-such; did any of you hear this hadith from the Prophet (peace and blessings be upon him)? They said: Yes, all of us have heard it. So they sent a man from that group with Sayyiduna Abdullah bin Qays (may Allah be pleased with him), until he came to Sayyiduna Umar (may Allah be pleased with him) and informed him of this hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13560