Jami` at-Tirmidhi, Book 49, Hadith 4005 (In-Book) ⓘ
Narrated Jabir bin Samurah: "The seal of the Messenger of Allah" - meaning the one which was between his two shoulder blades - "was fleshy and red, resembling the egg of a pigeon."
حَدَّثَنَا سَعِيدُ بْنُ يَعْقُوبَ الطَّالْقَانِيُّ، حَدَّثَنَا أَيُّوبُ بْنُ جَابِرٍ، عَنْ سِمَاكِ بْنِ حَرْبٍ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ كَانَ خَاتَمُ رَسُولِ اللَّهِ صلى الله عليه وسلم - يَعْنِي الَّذِي بَيْنَ كَتِفَيْهِ غُدَّةً حَمْرَاءَ مِثْلَ بَيْضَةِ الْحَمَامَةِ . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ .
also referenced under: Hadith 3644 (Reference) & Volume 6, Book 46, Hadith 3644 (DarusSalam)