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 ‏"‏ ‏.‏

It was narrated from Wasi' bin Habban that: He asked 'Abdullah bin 'Umar about the prayer of the Messenger of Allah (PBUH). 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." Translation Not Available

Book Ref: Sunan An Nisai Book 13 Hadith 1320
Web Ref:  Sunan An Nisai Vol 2 Book 13 Hadith 1321