Sahl said, "Al-Mundhir ibn Abi Usayd was brought to the Prophet, (ﷺ), when he was born and the Prophet (ﷺ) placed him on his thigh while Abu Usayd was seated near him. The Prophet, (ﷺ), was busy with something in front of him, so Abu Usayd told someone to take his son from the Prophet's leg. When the Prophet, (ﷺ), became aware of it, he asked, 'Where is the child?' Abu Usayd replied, 'We sent him home.' The Prophet (ﷺ) asked, 'What is his name?' He replied, 'Such-and-such.' The Prophet (ﷺ) said, 'No, rather his name is al-Mundhir.' So we called him al-Mundhir from that day."

حَدَّثَنَا سَعِيدُ بْنُ أَبِي مَرْيَمَ، قَالَ‏:‏ حَدَّثَنَا أَبُو غَسَّانَ قَالَ‏:‏ حَدَّثَنِي أَبُو حَازِمٍ، عَنْ سَهْلٍ قَالَ‏:‏ أُتِيَ بِالْمُنْذِرِ بْنِ أَبِي أُسَيْدٍ إِلَى النَّبِيِّ صلى الله عليه وسلم حِينَ وُلِدَ، فَوَضَعَهُ عَلَى فَخِذِهِ، وَأَبُو أُسَيْدٍ جَالِسٌ، فَلَهَى النَّبِيُّ صلى الله عليه وسلم بِشَيْءٍ بَيْنَ يَدَيْهِ، وَأَمَرَ أَبُو أُسَيْدٍ بِابْنِهِ فَاحْتُمِلَ مِنْ فَخِذِ النَّبِيِّ صلى الله عليه وسلم، فَاسْتَفَاقَ النَّبِيُّ صلى الله عليه وسلم فَقَالَ‏:‏ أَيْنَ الصَّبِيُّ‏؟‏ فَقَالَ أَبُو أُسَيْدٍ‏:‏ قَلَبْنَاهُ يَا رَسُولَ اللهِ، قَالَ‏:‏ مَا اسْمُهُ‏؟‏ قَالَ‏:‏ فُلاَنٌ، قَالَ‏:‏ لاَ، لَكِنِ اسْمُهُ الْمُنْذِرُ، فَسَمَّاهُ يَوْمَئِذٍ الْمُنْذِرَ‏.‏