Sunan an-Nasa'i 1157
سنن النسائي#1157SahihIt was narrated from 'Abdullah bin 'Abdullah bin 'Umar that his father said:"One of the sunnahs of the prayer is to spread your left foot beneath you, and hold your right foot upright
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 Bukhari
In-book reference: 12:129