There was a treaty between Muawiya and the Romans, and he was advancing through their territory so that the moment the treaty expired, he could launch a raid against them. Suddenly a man on a riding beast, or on a horse, was seen calling out, "Allah is the greatest! Faithfulness, not treachery!" The man turned out to be Amr bin Abasa.Muawiya asked him about what he had said.He replied, "I heard the Messenger of Allah ﷺ say, 'Whoever has a treaty with a people must not break it nor tighten its terms until its term has run out, or else he must openly renounce it to them on equal notice.'"So Muawiya turned back with the army.
حدثنا محمود بن غيلان حدثنا أبو داود قال أنبأنا شعبة قال أخبرني أبو الفيض قال
كان بين معاوية وبين أهل الروم عهد وكان يسير في بلادهم حتى إذا انقضى العهد أغار عليهم فإذا 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 عهدا ولا يشدنه حتى يمضي أمده أو ينبذ إليهم على سواء قال فرجع معاوية بالناس
Its isnad is sahih. Abu Dawud narrated it in the Book of Jihad, in the chapter on an imam who has a covenant with the enemy going on an expedition against them, hadith no. 2759, from the hadith of Shubah with the same wording. It is also found in Musnad Tayalisi, hadith no. 1155, and Ibn Hibban graded it sahih, hadith no. 1681.