[Machine] The Prophet ﷺ used to straighten up in sujood (prostration) until he could see the one behind him and his armpits became visible.  

كَانَ النَّبِيُّ ﷺ «إِذَا سَجَدَ جَافَى حَتَّى يَرَى مَنْ خَلْفَهُ وَضَحَ إِبِطَيْهِ»  

[Machine] The translation of the given sentence is as follows: "The Messenger of Allah ﷺ used to be so humble in his prostration that if she (a camel) wanted to pass beneath him, it could."  

كَانَ رَسُولُ اللَّهِ ﷺ «إِذَا سَجَدَ جَافَى حَتَّى لَوْ شَاءَتْ بَهْمَةٌ تَمُرُّ تَحْتَهُ لَمَرَّتْ»  

When the Messenger of Allah ﷺ prostrated himself, he spread his arms, i. e. he separated them so much that the whiteness of his armpits became visible from behind and when he sat (for Jalsa) he rested on his left thigh. (Using translation from Muslim 497a)  

عَنْ مَيْمُونَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ كَانَ رَسُولُ اللَّهِ ﷺ إِذَا سَجَدَ خَوَّى بِيَدَيْهِ يَعْنِي جَنَّحَ حَتَّى يُرَى وَضَحُ إِبْطَيْهِ مِنْ وَرَائِهِ وَإِذَا قَعَدَ اطْمَأَنَّ عَلَى فَخِذِهِ الْيُسْرَى