There was a treaty between Muawiya and the Byzantines, and he was marching toward their lands so that when the treaty expired he could attack them. Then a man came on a horse, or perhaps a mule, saying, "Allah is greatest, Allah is greatest. Let there be faithfulness, not treachery."When they looked, it was Amr bin Abasa. Muawiya sent for him and questioned him.He said, "I heard the Messenger of Allah ﷺ say, 'Whoever has a treaty between himself and a people must not tighten its knot nor loosen it until its term has expired, or else he must openly renounce it to them on equal terms.'"So Muawiya turned back.
حدثنا حفص بن عمر النمري قال حدثنا شعبة عن أبي الفيض
كان بين معاوية وبين الروم عهد وكان يسير نحو بلادهم حتى إذا انقضى العهد غزاهم فجاء رجل على فرس أو برذون وهو يقول الله أكبر الله أكبر وفاء لا غدر فنظروا فإذا عمرو بن عبسة فأرسل إليه معاوية فسأله فقال سمعت رسول الله ﷺ يقول من كان بينه وبين قوم عهد فلا يشد عقدة ولا يحلها حتى ينقضي أمدها أو ينبذ إليهم على سواء فرجع معاوية