It was narrated that Wasi' bin Habban said:"I said to Ibn 'Umar: "Tell me about the prayer of the Messenger of Allah (ﷺ); how was it?" He mentioned the takbir and he mentioned: As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) to his right and: As-salamu 'alaykum (peace be upon you) to his left."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبْدُ الْعَزِيزِ، - يَعْنِي الدَّرَاوَرْدِيَّ - عَنْ عَمْرِو بْنِ يَحْيَى، عَنْ مُحَمَّدِ بْنِ يَحْيَى بْنِ حَبَّانَ، عَنْ عَمِّهِ، وَاسِعِ بْنِ حَبَّانَ، قَالَ قُلْتُ لاِبْنِ عُمَرَ أَخْبِرْنِي عَنْ صَلاَةِ، رَسُولِ اللَّهِ صلى الله عليه وسلم كَيْفَ كَانَتْ قَالَ فَذَكَرَ التَّكْبِيرَ قَالَ يَعْنِي وَذَكَرَ " السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ" عَنْ يَمِينِهِ, "السَّلاَمُ عَلَيْكُمْ" عَنْ يَسَارِهِ."
Nesai
The Book of Forgetfulness (In Prayer) • Hadith 1321