Sahl b. Sa'd reported that Mundhir b. Aba Usaid was brought to Allah's Messenger (ﷺ) at the time of his birth Allah's. Messenger (ﷺ) placed him on his thigh and Abfi Usaid kept sitting there. Allah's Messenger (ﷺ) had been occupied with something else before him. Abu Usaid commanded his child to be lifted from the lap of Allah's Messenger (ﷺ) and so he was lifted. When Allah's Messenger (ﷺ) had finished the work he said:

Where is the child? Abd Usaid said: Allah's Messenger (ﷺ) , we took him away. He said: What is his name? He said; Allah's Messenger (ﷺ) , it is so and so, whereupon he (the Prophet) said: Nay, his name is Mundhir, and named him Mundhir on that day.

حَدَّثَنِي مُحَمَّدُ بْنُ سَهْلٍ التَّمِيمِيُّ، وَأَبُو بَكْرِ بْنُ إِسْحَاقَ قَالاَ حَدَّثَنَا ابْنُ أَبِي مَرْيَمَ، حَدَّثَنَا مُحَمَّدٌ، - وَهُوَ ابْنُ مُطَرِّفٍ أَبُو غَسَّانَ - حَدَّثَنِي أَبُو حَازِمٍ، عَنْ سَهْلِ بْنِ سَعْدٍ، قَالَ أُتِيَ بِالْمُنْذِرِ بْنِ أَبِي أُسَيْدٍ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم حِينَ وُلِدَ فَوَضَعَهُ النَّبِيُّ صلى الله عليه وسلم عَلَى فَخِذِهِ وَأَبُو أُسَيْدٍ جَالِسٌ فَلَهِيَ النَّبِيُّ صلى الله عليه وسلم بِشَىْءٍ بَيْنَ يَدَيْهِ فَأَمَرَ أَبُو أُسَيْدٍ بِابْنِهِ فَاحْتُمِلَ مِنْ عَلَى فَخِذِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَأَقْلَبُوهُ فَاسْتَفَاقَ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏"‏ أَيْنَ الصَّبِيُّ ‏"‏ ‏.‏ فَقَالَ أَبُو أُسَيْدٍ أَقْلَبْنَاهُ يَا رَسُولَ اللَّهِ ‏.‏ فَقَالَ ‏"‏ مَا اسْمُهُ ‏"‏ ‏.‏ قَالَ فُلاَنٌ يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ لاَ وَلَكِنِ اسْمُهُ الْمُنْذِرُ ‏"‏ ‏.‏ فَسَمَّاهُ يَوْمَئِذٍ الْمُنْذِرَ ‏.‏