Jami` at-Tirmidhi 2721
Narrated Abu Tamimah Al-Hujaimi:
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.'"
حَدَّثَنَا سُوَيْدٌ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا خَالِدٌ الْحَذَّاءُ، عَنْ أَبِي تَمِيمَةَ الْهُجَيْمِيِّ، عَنْ رَجُلٍ، مِنْ قَوْمِهِ قَالَ طَلَبْتُ النَّبِيَّ صلى الله عليه وسلم فَلَمْ أَقْدِرْ عَلَيْهِ فَجَلَسْتُ فَإِذَا نَفَرٌ هُوَ فِيهِمْ وَلاَ أَعْرِفُهُ وَهُوَ يُصْلِحُ بَيْنَهُمْ فَلَمَّا فَرَغَ قَامَ مَعَهُ بَعْضُهُمْ فَقَالُوا يَا رَسُولَ اللَّهِ ‏.‏ فَلَمَّا رَأَيْتُ ذَلِكَ قُلْتُ عَلَيْكَ السَّلاَمُ يَا رَسُولَ اللَّهِ عَلَيْكَ السَّلاَمُ يَا رَسُولَ اللَّهِ عَلَيْكَ السَّلاَمُ يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ إِنَّ عَلَيْكَ السَّلاَمُ تَحِيَّةُ الْمَيِّتِ إِنَّ عَلَيْكَ السَّلاَمُ تَحِيَّةُ الْمَيِّتِ ‏"‏ ‏.‏ ثَلاَثًا ثُمَّ أَقْبَلَ عَلَىَّ فَقَالَ ‏"‏ إِذَا لَقِيَ الرَّجُلُ أَخَاهُ الْمُسْلِمَ فَلْيَقُلِ السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ ‏"‏ ‏.‏ ثُمَّ رَدَّ عَلَىَّ النَّبِيُّ صلى الله عليه وسلم قَالَ ‏"‏ وَعَلَيْكَ وَرَحْمَةُ اللَّهِ وَعَلَيْكَ وَرَحْمَةُ اللَّهِ وَعَلَيْكَ وَرَحْمَةُ اللَّهِ ‏"‏ ‏.‏ 
قَالَ أَبُو عِيسَى وَقَدْ رَوَى هَذَا الْحَدِيثَ أَبُو غِفَارٍ، عَنْ أَبِي تَمِيمَةَ الْهُجَيْمِيِّ، عَنْ أَبِي جُرَىٍّ، جَابِرِ بْنِ سُلَيْمٍ الْهُجَيْمِيِّ قَالَ أَتَيْتُ النَّبِيَّ صلى الله عليه وسلم فَذَكَرَ الْحَدِيثَ ‏.‏ وَأَبُو تَمِيمَةَ اسْمُهُ طَرِيفُ بْنُ مُجَالِدٍ ‏.