Sunan an-Nasa'i, Volume 2, Book 13, Hadith 1286 (DarusSalam) ⓘ
It was narrated that Abu Mas'ud Al-Ansari siad: "The Messenger of Allah came to us in the Majlis of Sa'd bin 'Ubadah and Bashir bin Sa'd said to him: 'Allah has commanded us to send Salah upon you, O Messenger of Allah; so how should we send salah upon you?' The Messenger of Allah remained silent until we wished that he had not asked him. Then he said: 'Say: 'Alahumma salli 'ala Muhammad wa 'ala ali Muhammad, kama sallaita 'ala Ibrahima wa barik 'ala Muhammad kama barakta 'ala ali Ibrahim fil-'alamin, innaka hamidun majid (O Allah, send salah upon Muhammad and upon the family of Muhammad, as You sent salah upon the family of Ibrahim, and send blessings upon Muhammad and upon the family of Muhammad as You sent blessings upon the family of Ibrahim among the nations. You are indeed Worthy of praise, Full of glory.)" And the salam is as you know.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، وَالْحَارِثُ بْنُ مِسْكِينٍ، قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ، - وَاللَّفْظُ لَهُ - عَنِ ابْنِ الْقَاسِمِ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ نُعَيْمِ بْنِ عَبْدِ اللَّهِ الْمُجْمِرِ، أَنَّ مُحَمَّدَ بْنَ عَبْدِ اللَّهِ بْنِ زَيْدٍ الأَنْصَارِيَّ، - وَعَبْدُ اللَّهِ بْنُ زَيْدٍ الَّذِي أُرِيَ النِّدَاءَ بِالصَّلاَةِ - أَخْبَرَهُ عَنْ أَبِي مَسْعُودٍ الأَنْصَارِيِّ، أَنَّهُ قَالَ أَتَانَا رَسُولُ اللَّهِ صلى الله عليه وسلم فِي مَجْلِسِ سَعْدِ بْنِ عُبَادَةَ فَقَالَ لَهُ بَشِيرُ بْنُ سَعْدٍ أَمَرَنَا اللَّهُ عَزَّ وَجَلَّ أَنْ نُصَلِّيَ عَلَيْكَ يَا رَسُولَ اللَّهِ فَكَيْفَ نُصَلِّي عَلَيْكَ فَسَكَتَ رَسُولُ اللَّهِ صلى الله عليه وسلم حَتَّى تَمَنَّيْنَا أَنَّهُ لَمْ يَسْأَلْهُ ثُمَّ قَالَ " قُولُوا اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا صَلَّيْتَ عَلَى آلِ إِبْرَاهِيمَ وَبَارِكْ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا بَارَكْتَ عَلَى آلِ إِبْرَاهِيمَ فِي الْعَالَمِينَ إِنَّكَ حَمِيدٌ مَجِيدٌ وَالسَّلاَمُ كَمَا عَلِمْتُمْ " .
also referenced under: Hadith 1285 (Reference) & Book 13, Hadith 107 (In-Book)