Sunan Abi Dawud, Hadith 4748

The tradition mentioned above has also been transmitted by Anas through a different chain of narrators in a similar manner. This version adds; Their sign is shaving the head and eliminating the hair. If you see them, kill them. Abu Dawud said: Tasmid means uprooting the hair.

حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَحْوَهُ قَالَ ‏:‏ ‏ "‏ سِيمَاهُمُ التَّحْلِيقُ وَالتَّسْبِيدُ، فَإِذَا رَأَيْتُمُوهُمْ فَأَنِيمُوهُمْ ‏" ‏ ‏.‏ قَالَ أَبُو دَاوُدَ ‏:‏ التَّسْبِيدُ اسْتِئْصَالُ الشَّعْرِ ‏.‏

sunnah.com

also referenced under: Hadith 4766 (DarusSalam)