`Ilbaa bin Ahmar Al-yashkari says that the Sahaabi, Abu Zayd `Amr bin Akhtab Al-Ansaari may Allah be pleased with him said to me:
"Messenger of Allah ﷺ once asked me to massage his waist. When I began massaging the back, accidentally (by chance) my fingers touched the Seal of Prophethood. `Ilbaa (may Allah be pleased with him) says: `I asked Amr (may Allah be pleased with him), what is the Seal of Prophethood?' He replied: `It was a collection of few hair'".

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ: حَدَّثَنَا أَبُو عَاصِمٍ، قَالَ: حَدَّثَنَا عَزْرَةُ بْنُ ثَابِتٍ، قَالَ: حَدَّثَنِي عِلْبَاءُ بْنُ أَحْمَرَ الْيَشْكُرِيُّ، قَالَ: حَدَّثَنِي أَبُو زَيْدٍ عَمْرُو بْنُ أَخْطَبَ الأَنْصَارِيُّ، قَالَ: قَالَ لِي رَسُولُ اللهِ ﷺ: يَا أَبَا زَيْدٍ، ادْنُ مِنِّي فَامْسَحْ ظَهْرِي، فَمَسَحْتُ ظَهْرَهُ، فَوَقَعَتْ أَصَابِعِي عَلَى الْخَاتَمِ قُلْتُ: وَمَا الْخَاتَمُ؟ قَالَ: شَعَرَاتٌ مُجْتَمِعَاتٌ.