Narrated Anas bin Malik:While the Prophet (ﷺ) was in the market, somebody, called, "O Abul-Qasim." The Prophet (ﷺ) turned to him. The man said, "I have called to this (i.e. another man)." The Prophet (ﷺ) said, "Name yourselves by my name but not by my Kunya (name)." (In Arabic world it is the custom to call the man as the father of his eldest son, e.g. Abul-Qasim.) (See Hadith No. 737, Vol. 4)
حَدَّثَنَا آدَمُ بْنُ أَبِي إِيَاسٍ، حَدَّثَنَا شُعْبَةُ، عَنْ حُمَيْدٍ الطَّوِيلِ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم فِي السُّوقِ، فَقَالَ رَجُلٌ يَا أَبَا الْقَاسِمِ. فَالْتَفَتَ إِلَيْهِ النَّبِيُّ صلى الله عليه وسلم فَقَالَ إِنَّمَا دَعَوْتُ هَذَا. فَقَالَ النَّبِيُّ صلى الله عليه وسلم " سَمُّوا بِاسْمِي، وَلاَ تَكَنَّوْا بِكُنْيَتِي ".
Bukhari
Sales and Trade • Hadith 73