Musannaf Ibn Abi Shayba 27:774

Yahya ibn Ya'la al-Taymi narrated to us, from 'Abd al-Malik ibn 'Umayr, from Qabisa ibn Jabir, who said: 'Umar addressed us at the gate of al-Jabiya and said: "Indeed, the Messenger of Allah (may Allah bless him and grant him peace) stood among us just as I am standing among you. Then he said: 'O people, fear Allah regarding my companions, then those who follow them, then those who follow them. Then fear lying and false testimonies.'"