Sunan an-Nasa'i, Volume 2, Book 12, Hadith 1110 (DarusSalam) ⓘ

It was narrated from Maimunah that: When the Prophet prostrated he would hold his arms out from his sides so that if a lamb wanted to pass beneath his arms it would be able to do so.

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عُبَيْدِ اللَّهِ، - وَهُوَ ابْنُ عَبْدِ اللَّهِ بْنِ الأَصَمِّ - عَنْ عَمِّهِ، يَزِيدَ - وَهُوَ ابْنُ الأَصَمِّ - عَنْ مَيْمُونَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ إِذَا سَجَدَ جَافَى يَدَيْهِ حَتَّى لَوْ أَنَّ بَهْمَةً أَرَادَتْ أَنْ تَمُرَّ تَحْتَ يَدَيْهِ مَرَّتْ ‏.‏