Jami` at-Tirmidhi 270
جامع الترمذي#270SahihAbu Humaid As-Sa'idi narrated:"When the Prophet would prostrate, he placed his nose and his forehead on the ground, and he held his forearms away from his sides, and he placed his hands parallel to his shoulders
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiHasan
In-book reference: 2:122