Hadithcore
Sahih al-Bukhari, 6299
sahih

Narrated Said bin Jubair:

Ibn 'Abbas was asked, "How old were you when the Prophet (ﷺ) died?" He replied. "At that time I had been circumcised." At that time, people did not circumcise the boys till they attained the age of puberty. Sa'id bin Jubair said, "Ibn 'Abbas said, 'When the Prophet (ﷺ) died, I had already been circumcised. "

حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ الرَّحِيمِ، أَخْبَرَنَا عَبَّادُ بْنُ مُوسَى، حَدَّثَنَا إِسْمَاعِيلُ بْنُ جَعْفَرٍ، عَنْ إِسْرَائِيلَ، عَنْ أَبِي إِسْحَاقَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، قَالَ سُئِلَ ابْنُ عَبَّاسٍ مِثْلُ مَنْ أَنْتَ حِينَ قُبِضَ النَّبِيُّ صلى الله عليه وسلم قَالَ أَنَا يَوْمَئِذٍ مَخْتُونٌ‏.‏ قَالَ وَكَانُوا لاَ يَخْتِنُونَ الرَّجُلَ حَتَّى يُدْرِكَ‏.‏

References2 variants
In-Book Reference
Book 79, Hadith 71
USC-MSA web (English) reference
Vol. 8, Book 74, Hadith 313 (deprecated numbering scheme)