Sunan an-Nasa'i 812
سنن النسائي#812SahihIt was narrated that Abu Mas'ad Al-Ansari said:"The Messenger of Allah (ﷺ) used to gently pat our shoulders (to make sure the row was straight) at the time of prayer, and he would say: 'Keep (the rows) straight; do not differ from one another lest your hearts should suffer from discord. Let those who are mature and wise stand closest to me, then those who are next to them, then those who are next to them
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 10:36