A man amongst us begot a boy whom he named Al-Qasim. On that the Ansar said, (to the man), "We will never call you Abu-al-Qasim and will never please you with this blessed title." So, he went to the Prophet and said, "O Messenger of Allah ﷺ! I have begotten a boy whom I named Al-Qasim and the Ansar said, 'We will never call you Abu-al-Qasim, nor will we please you with this title.' " The Prophet ﷺ said, "The Ansar have done well. Name by my name, but do not name by my Kunya, for I am Qasim."
وُلِدَ لِرَجُلٍ مِنَّا غُلاَمٌ فَسَمَّاهُ الْقَاسِمَ فَقَالَتِ الأَنْصَارُ لاَ نَكْنِيكَ أَبَا الْقَاسِمِ وَلاَ نُنْعِمُكَ عَيْنًا فَأَتَى النَّبِيَّ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ وُلِدَ لِي غُلاَمٌ فَسَمَّيْتُهُ الْقَاسِمَ فَقَالَتِ الأَنْصَارُ لاَ نَكْنِيكَ أَبَا الْقَاسِمِ وَلاَ نُنْعِمُكَ عَيْنًا فَقَالَ النَّبِيُّ ﷺ أَحْسَنَتِ الأَنْصَارُ سَمُّوا بِاسْمِي وَلاَ تَكَنَّوْا بِكُنْيَتِي فَإِنَّمَا أَنَا قَاسِمٌ