Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) said that al-Mundhir bin Abi Usayd was brought to the Messenger of Allah (peace and blessings be upon him) when he was born, and he (peace and blessings be upon him) placed him on his thigh while Abu Usayd (may Allah be pleased with him) was sitting there. The narrator said: The attention of the Prophet (peace and blessings be upon him) was drawn to something in front of him, so Abu Usayd (may Allah be pleased with him) gave instructions about his son, and he was carried away from the Prophet (peace and blessings be upon him); they took him back home. Then the Prophet (peace and blessings be upon him) missed him and said: "Where is the child?" Abu Usayd (may Allah be pleased with him) said: O Messenger of Allah, we have taken him back. He (peace and blessings be upon him) asked: "What is his name?" He said: So-and-so. He (peace and blessings be upon him) said: "No, rather his name is al-Mundhir." So he (peace and blessings be upon him) named him al-Mundhir that day.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5772