Mishkat al-Masabih 3980
Sulaim b. ‘Amir said:
There was a covenant between Mu'awiya and the Byzantines, and he was going towards their country; then when the covenant came to an end he attacked them. A man came on a horse, or a packhorse, saying, “God is most great, God is most great; let there be faithfulness and not treachery.”* And when they looked they found that he was 'Amr b. ‘Abasa. Mu'awiya questioned him about that and he replied that he had heard God’s Messenger say, "When one has a covenant with people he must not loosen or strengthen it till its term comes, or he brings it to an end in agreement with them.” He said that Mu'awiya then took the people back. 

* Mirqat , 4, 255 says that 'Amr b. ‘Abasa felt it was an act of treachery to make a treaty while in one’s own country and then approach the enemy’s country when the period of the treaty was near an end, so as to be able to make an immediate attack.

Tirmidhi and Abu Dawud transmitted it.
وَعَنْ سُلَيْمِ بْنِ عَامِرٍ قَالَ: كَانَ بَيْنَ مُعَاوِيَةَ وَبَيْنَ الرُّومِ عَهْدٌ وَكَانَ يَسِيرُ نَحْوَ بِلَادِهِمْ حَتَّى إِذَا انْقَضَى الْعَهْدُ أَغَارَ عَلَيْهِمْ فَجَاءَ رَجُلٌ عَلَى فَرَسٍ أَوْ بِرْذَوْنٍ وَهُوَ يَقُولُ: اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ وَفَاءٌ لَا غدر فَنظر فَإِذا هُوَ عَمْرو ابْن عَبَسَةَ فَسَأَلَهُ مُعَاوِيَةُ عَنْ ذَلِكَ فَقَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُول: «مَنْ كَانَ بَيْنَهُ وَبَيْنَ قَوْمٍ عَهْدٌ فَلَا يَحُلَّنَّ عَهْدًا وَلَا يَشُدَّنَّهُ حَتَّى يُمْضِيَ أَمَدَهُ أَوْ يَنْبِذَ إِلَيْهِمْ عَلَى سَوَاءٍ» . قَالَ: فَرَجَعَ مُعَاوِيَة بِالنَّاسِ. رَوَاهُ التِّرْمِذِيّ وَأَبُو دَاوُد