(54) باب إِقَامَةِ الصُّلْبِ فِي السُّجُودِ
It was narrated that Abu Mas'ud said:
"The Messenger of Allah (ﷺ) said: 'No prayer is valid in which a man does not maintain his back (at ease) when bowing and prostrating.'" (DE)
Reference (DE): Sunan an-Nasa'i 1111 (DE)
In-book reference (DE): Book 12, Hadith 83 (DE)
English translation (DE): Vol. 2, Book 12, Hadith 1112 (DE)