Sulaym ibn Amir, a man of Himyar, said: There was a covenant between Mu'awiyah and the Byzantines, and he was going towards their country, and when the covenant came to an end, he attacked them. A man came on a horse, or a packhorse saying, Allah is Most Great, Allah is Most Great; let there be faithfulness and not treachery. And when they looked they found that he was Amr ibn Abasah. Mu'awiyah sent for him and questioned him (about that). He said: I heard the Messenger of Allah ﷺ say: When one has covenant with people he must not strengthen or loosen it till its term comes to an end or he brings it to an end in agreement with them (to make both the parties equal). So Mu'awiyah returned.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مَنْ كَانَ بَيْنَهُ وَبَيْنَ قَوْمٍ عَهْدٌ فَلاَ يَشُدُّ عُقْدَةً وَلاَ يَحُلُّهَا حَتَّى يَنْقَضِيَ أَمَدُهَا أَوْ يَنْبِذَ إِلَيْهِمْ عَلَى سَوَاءٍ فَرَجَعَ مُعَاوِيَةُ  

"I heard Sulaim bin 'Amir saying: 'There was a treaty between Mu'awiyah and the people of Rome. He was making an expedition into their lands so that when the period of the treaty was expires he would attack them. So when a man upon an animal' - or - 'upon a horse said: "Allahu Akbar! Fulfillment not betrayal!" - and it turned out to be 'Amr bin 'Abasah - Mu'awiyah asked him about that. He said: "I heard the Messenger of Allah ﷺ said: 'Whoever has a treaty between himself and a people, then let him not violate the treaty nor try to change it until its time has passed, or , in retribution for a similar offense.'" He said: "So Mu'awiyah returned with the people."  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مَنْ كَانَ بَيْنَهُ وَبَيْنَ قَوْمٍ عَهْدٌ فَلاَ يَحُلَّنَّ عَهْدًا وَلاَ يَشُدَّنَّهُ حَتَّى يَمْضِيَ أَمَدُهُ أَوْ يَنْبِذَ إِلَيْهِمْ عَلَى سَوَاءٍ قَالَ فَرَجَعَ مُعَاوِيَةُ بِالنَّاسِ  

"مَنْ كان بينهُ وبَينَ قوْمٍ عَهْدٌ فلا يَشُدَّ عُقْدَةً، وَلَا يَحُلَّهَا حَتَّى يَنْقَضِي أَمدُهَا، أَوْ يَنْبِذ إِليهِمْ عَلَى سواءٍ".