Sunan an-Nasa'i, Book 13, Hadith 142 (In-Book) ⓘ

It was narrated from Wasi' bin Habban that: He asked 'Abdullah bin 'Umar about the prayer of the Messenger of Allah. He said: "Allahu Akbar" every time he went down and "Allahu Akbar" every time he came up, then he said: "As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) to his right and: As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) to his left."

أَخْبَرَنَا الْحَسَنُ بْنُ مُحَمَّدٍ الزَّعْفَرَانِيُّ، عَنْ حَجَّاجٍ، قَالَ ابْنُ جُرَيْجٍ أَنْبَأَنَا عَمْرُو بْنُ يَحْيَى، عَنْ مُحَمَّدِ بْنِ يَحْيَى بْنِ حَبَّانَ، عَنْ عَمِّهِ، وَاسِعِ بْنِ حَبَّانَ، ‏.‏ أَنَّهُ سَأَلَ عَبْدَ اللَّهِ بْنَ عُمَرَ عَنْ صَلاَةِ، رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ اللَّهُ أَكْبَرُ كُلَّمَا وَضَعَ اللَّهُ أَكْبَرُ كُلَّمَا رَفَعَ ثُمَّ يَقُولُ ‏ "‏ السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ عَنْ يَمِينِهِ السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ عَنْ يَسَارِهِ ‏" ‏ ‏.‏