Sahih al-Bukhari 3537
Sahih al-Bukhari · Book 61: Virtues and Merits of the Prophet (pbuh) and his Companions · The Kunya of the Prophet (saws)
Narrated Anas:
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ ، حَدَّثَنَا شُعْبَةُ ، عَنْ حُمَيْدٍ ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم فِي السُّوقِ فَقَالَ رَجُلٌ يَا أَبَا الْقَاسِمِ. فَالْتَفَتَ النَّبِيُّ صلى الله عليه وسلم فَقَالَ " سَمُّوا بِاسْمِي، وَلاَ تَكْتَنُوا بِكُنْيَتِي " .
While the Prophet (ﷺ) was in the market, a man called (somebody), "O Abu-l-Qasim!' The Prophet (ﷺ) turned to him and said "Name yourselves after me but do not call yourselves by my Kuniya."