Jami` at-Tirmidhi Book 42, Hadith 33
that a man gave the Salam to the Prophet (ﷺ) while he was urinating, but the Prophet (ﷺ) did not return the Salam to him."
"Two of my companions and I went and presented ourselves to the Companions of the Prophet (ﷺ), for our hearing and sight had gone from suffering (hunger and thirst). But there was no one who would accept us. So we went to the Prophet (ﷺ) and he brought us to his family where there were three goats. The Prophet (ﷺ) said: 'Milk these.' We milked them, and each person drank his share, and we put aside a share for the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) came during the night and gave the Salam such that it would not wake the sleeping person, and the one who was awake could hear it. Then he went to the Masjid to per form Salat. Then he went for his drink and drank it."
from a man among his people, who said: "I went looking for the Prophet (ﷺ) but I was not able to find him. So I sat down, and then I saw a group of people, and he was among them, but I did not recognize him. He was settling some matter between them so when he was finished, some of them stood up with him and they were saying: 'O Messenger of Allah.' When I saw that, I said: "'Alaikas-Salam (upon you be peace) O Messenger of Allah! 'Alaikas-Salam (upon you be peace) O Messenger of Allah! 'Alaikas-Salam (upon you be peace) O Messenger of Allah!' He replied: 'Indeed "'Alaikas-Salam (upon you be peace)" is the greeting for the dead.' Then he came toward me and said: 'When a man meets his Muslim brother then he should say: "As-Salamu 'Alaikum Wa Rahmatullahi Wa Barakatuh (peace be upon you, and the mercy and blessings of Allah)." Then the Prophet (ﷺ) responded to my greeting, he said: 'And may Allah's mercy be upon you, and may Allah's mercy be upon you, and may Allah's mercy be upon you.'"