Sunan Abi Dawud, Book 1, Hadith 356 (USC-MSA) ⓘ

'Uthaim b. Kulaib reported from his father (Kuthair) on the authority of his grandfather (Kulaib) that he came to the Prophet: I have embraced Islam. The Prophet said to him: Remove from yourself the hair that grew during of unbelief, saying "shave them". He further says that another person (other than the grandfather of 'Uthaim) reported to him that the Prophet said to another person who accompanied him: Remove from yourself the hair that grew during the period of unbelief and get yourself circumcised.

حَدَّثَنَا مَخْلَدُ بْنُ خَالِدٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، قَالَ أُخْبِرْتُ عَنْ عُثَيْمِ بْنِ كُلَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، أَنَّهُ جَاءَ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ قَدْ أَسْلَمْتُ ‏.‏ فَقَالَ لَهُ النَّبِيُّ صلى الله عليه وسلم ‏"‏ أَلْقِ عَنْكَ شَعْرَ الْكُفْرِ ‏"‏ ‏.‏ يَقُولُ احْلِقْ ‏.‏ قَالَ وَأَخْبَرَنِي آخَرُ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ لآخَرَ مَعَهُ ‏"‏ أَلْقِ عَنْكَ شَعْرَ الْكُفْرِ وَاخْتَتِنْ ‏"‏ ‏.‏