Sunan of Abu Dawood Book 15, Hadith 2759

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ النَّمَرِيُّ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي الْفَيْضِ، عَنْ سُلَيْمِ بْنِ عَامِرٍ، - رَجُلٍ مِنْ حِمْيَرَ - قَالَ كَانَ بَيْنَ مُعَاوِيَةَ وَبَيْنَ الرُّومِ عَهْدٌ وَكَانَ يَسِيرُ نَحْوَ بِلاَدِهِمْ حَتَّى إِذَا انْقَضَى الْعَهْدُ غَزَاهُمْ فَجَاءَ رَجُلٌ عَلَى فَرَسٍ أَوْ بِرْذَوْنٍ وَهُوَ يَقُولُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ وَفَاءٌ لاَ غَدْرٌ فَنَظَرُوا فَإِذَا عَمْرُو بْنُ عَبَسَةَ فَأَرْسَلَ إِلَيْهِ مُعَاوِيَةُ فَسَأَلَهُ فَقَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ مَنْ كَانَ بَيْنَهُ وَبَيْنَ قَوْمٍ عَهْدٌ فَلاَ يَشُدُّ عُقْدَةً وَلاَ يَحُلُّهَا حَتَّى يَنْقَضِيَ أَمَدُهَا أَوْ يَنْبِذَ إِلَيْهِمْ عَلَى سَوَاءٍ ‏"‏ ‏.‏ فَرَجَعَ مُعَاوِيَةُ ‏.‏

Narrated Amr ibn Abasah: 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