Sahih Muslim , Book 30, Hadith 5790 (USC-MSA) ⓘ
Jabir. Samura reported: I saw the seal on his back as if it were a pigeon's egg.
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ سِمَاكٍ، قَالَ سَمِعْتُ جَابِرَ بْنَ سَمُرَةَ، قَالَ رَأَيْتُ خَاتِمًا فِي ظَهْرِ رَسُولِ اللَّهِ صلى الله عليه وسلم كَأَنَّهُ بَيْضَةُ حَمَامٍ .
also referenced under: Book 43, Hadith 143 (In-Book) & Hadith 2344 (Reference)