ʿAli ؓ said: O Messenger of Allah ﷺ, if I have a son after you are gone, I will call him by your name and give him your kunyah. He said: ʿYes.ʿ That was a concession from the Messenger of Allah ﷺ to ʿAli.
عَلِيٌّ يَا رَسُولَ اللهِ أَرَأَيْتَ إِنْ وُلِدَ لِي بَعْدَكَ وَلَدٌ أُسَمِّيهِ بِاسْمِكَ وَأُكَنِّيهِ بِكُنْيَتِكَ؟ قَالَ نَعَمْ فَكَانَتْ رُخْصَةً مِنْ رَسُولِ اللهِ ﷺ لِعَلِيٍّ