Sulaym ibn Aamir reported that a peace treaty existed between Mu’awiyah (RA) and the people of Rome. He advanced towards them with the intention to attack them the moment the treaty expired. Suddenly, a rider on a beast or, horse rider came rushing and calling out, ‘Allahu Akbar! Faithfulness, not betrayal.” He was Amr ibn Abasah Mu’awiyah asked him about it and he said, “1 had heard Allah’s Messenger (SAW) say, “If anyone has a covenant with a people then it is not lawful for him to violate it or alter it till its expiry, or he should throw it towards them that they may know that it is rescinded.’ So, Mu’awiyah retreated.
[Abu Dawud 2759, Ahmed 17012]