Musnad Abu Ya'la al-Mawsili 115:122

Suwayd ibn Sa'id narrated to us, al-Walid ibn Muslim narrated to us, from al-Awza'i, from Qatadah, from Anas, that the Prophet (peace be upon him) said: "There will be disagreement and division in my nation. They will speak well and act poorly. They will recite the Qur'an, but it will not pass beyond their collarbones. One of you will belittle his own prayer compared to their prayer, and his own fasting compared to their fasting. They are the worst of the creation and the creatures. So, glad tidings to whoever kills them and whom they kill. They call to the Book of Allah, while they have no part in it. Whoever kills them is closer to Allah than they are." They said, "O Messenger of Allah, what is their sign?" He said, "Shaving [the head]."