Narrated Sahl:

When Al-Mundhir bin Abu Usaid was born, he was brought to the Prophet who placed him on his thigh. While Abu Usaid was sitting there, the Prophet was busy with something in his hands so Abu Usaid told someone to take his son from the thigh of the Prophet . When the Prophet finished his job (with which he was busy), he said, "Where is the boy?" Abu Usaid replied, "We have sent him home." The Prophet ﷺ said, "What is his name?" Abu Usaid said, "(His name is) so-and-so. " The Prophet ﷺ said, "No, his name is Al-Mundhir." So he called him Al-Mundhir from that day.

حَدَّثَنَا سَعِيدُ بْنُ أَبِي مَرْيَمَ، حَدَّثَنَا أَبُو غَسَّانَ، قَالَ حَدَّثَنِي أَبُو حَازِمٍ، عَنْ سَهْلٍ، قَالَ أُتِيَ بِالْمُنْذِرِ بْنِ أَبِي أُسَيْدٍ إِلَى النَّبِيِّ ﷺ حِينَ وُلِدَ، فَوَضَعَهُ عَلَى فَخِذِهِ وَأَبُو أُسَيْدٍ جَالِسٌ، فَلَهَا النَّبِيُّ ﷺ بِشَىْءٍ بَيْنَ يَدَيْهِ، فَأَمَرَ أَبُو أُسَيْدٍ بِابْنِهِ فَاحْتُمِلَ مِنْ فَخِذِ النَّبِيِّ ﷺ فَاسْتَفَاقَ النَّبِيُّ ﷺ فَقَالَ " أَيْنَ الصَّبِيُّ ". فَقَالَ أَبُو أُسَيْدٍ قَلَبْنَاهُ يَا رَسُولَ اللَّهِ. قَالَ " مَا اسْمُهُ ". قَالَ فُلاَنٌ. قَالَ " وَلَكِنْ أَسْمِهِ الْمُنْذِرَ ". فَسَمَّاهُ يَوْمَئِذٍ الْمُنْذِرَ.