Musannaf Ibn Abi Shayba 28:880

Waki’ ibn al-Jarrah narrated to us, he said: Shu’bah narrated to us, from Abu al-Fayd, from Sulaym ibn ‘Amir, who said: There was a treaty between Mu’awiyah and his people [the Byzantines]. Mu’awiyah set out traveling in their land so that when the treaty expired, he would launch a raid upon them. Suddenly, a man was calling out from the side of the camp: "Fulfillment, not treachery! Fulfillment, not treachery!" It was ‘Amr ibn ‘Abasah. He said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: "Whoever has a treaty between himself and a people, let him not break his treaty, nor untie it, until its term expires or he notifies them [of the termination] on equal terms."