Salim bin Amir reported,

There was a treaty between Muawiya and the Byzantines, and he was advancing through their lands so that once the treaty expired he could launch a raid against them. Suddenly a man appeared on a beast, or on a horse, calling out, "Allah is the Greatest! Faithfulness, not treachery!" It turned out to be Amr bin Abasa.Muawiya asked him about what he meant, and he replied, "I heard the Messenger of Allah ﷺ say, 'Whoever has a treaty between himself and a people must not loosen its knot nor tighten it until its term has run out, or else he must openly renounce it to them on equal terms.'"So Muawiya turned back with the army.

عن سليم بن عامر قال

كان بين معاوية وبين الروم عهد، وكان يسير في بلادهم حتى إذا انقضى العهد أغار عليهم، وإذا رجل على دابة، أو على فرس وهو يقول: الله أكبر وفاء لا غدر، وإذا هو عمرو بن عبسة، فسأله معاوية عن ذلك، فقال: سمعت رسول الله ﷺ يقول: من كان بينه وبين قوم عهد، فلا يحلن عقدة ولا يشدها حتى يمضي أمده، أو ينبذ إليهم على سواء فرجع معاوية بالناس.