Musannaf Ibn Abi Shaybah 35346 — Those whom it is forbidden to kill

Sayyiduna Abu Bakr (may Allah be pleased with him) sent out an army and said to it: Fight in the name of Allah. O Allah, make their death a martyrdom in Your path. Then he said: You will come upon people in their hermitages; leave them and what they have devoted themselves to. And you will come upon people who have shaved the middle of their heads, leaving what looks like bands; strike what they have shaved from the middle of their heads.