Imam Ahmad : 12660

حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ عَنْ حُمَيْدٍ عَنْ أَنَسٍ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يُحِبُّ أَنْ يَلِيَهُ فِي الصَّلَاةِ الْمُهَاجِرُونَ وَالْأَنْصَارُ لِيَحْفَظُوا عَنْهُ

Narrated to us by [Ibn Abu 'Adi] from [Humaid] from [Anas], The Messenger of Allah shallahu'alaihi wasallam likes it if those behind his prayers are the muhajirin and ansar, so that they preserve the way he prays.