When al-Hasan was born, I named him Hamzah. When al-Husain was born, I named him after his paternal uncle Jaʿfar. Then the Messenger of Allah ﷺ called me and said: ʿI have been commanded to change the names of these two.ʿ I said: Allah and His Messenger know best. And he named them Hasan and Husain. ؓ
لَمَّا وُلِدَ الْحَسَنُ سَمَّاهُ حَمْزَةَ فَلَمَّا وُلِدَ الْحُسَيْنُ سَمَّاهُ بِعَمِّهِ جَعْفَرٍ قَالَ فَدَعَانِي رَسُولُ اللهِ ﷺ فَقَالَ إِنِّي أُمِرْتُ أَنْ أُغَيِّرَ اسْمَ هَذَيْنِ فَقُلْتُ اللهُ وَرَسُولُهُ أَعْلَمُ فَسَمَّاهُمَا حَسَنًا وَحُسَيْنًا