From Sahih Bukhari (Hadith 6299):
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 died, I had already been circumcised
Reference: Bukhari 6299