Sunan an-Nasa'i 3780
It was narrated that Abu Musa Al-Ash'ari said:
"I came to the Messenger of Allah with a group of the Ash'ari people and asked him to give us animals to ride. He said: 'By Allah, I cannot give you anything to ride and I have nothing to give you to ride.' We stayed as long as Allah willed, then some camels were brought to him. He ordered that we be given three fine-looking camels. When we left, we said to one another: 'We came to the Messenger of Allah to ask him for animals to ride, and he swore by Allah that he would not give us anything to ride, then he gave us something.'" Abu Musa said: "We came to the Prophet and told him about that. He said: 'I did not give you animals to ride, rather Allah gave you them to ride. By Allah, I do not swear an oath and then see something better than it, but I offer expiation for my oath and do that which is better.'"
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ غَيْلاَنَ بْنِ جَرِيرٍ، عَنْ أَبِي بُرْدَةَ، عَنْ أَبِي مُوسَى الأَشْعَرِيِّ، قَالَ أَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فِي رَهْطٍ مِنَ الأَشْعَرِيِّينَ نَسْتَحْمِلُهُ فَقَالَ ‏"‏ وَاللَّهِ لاَ أَحْمِلُكُمْ وَمَا عِنْدِي مَا أَحْمِلُكُمْ ‏"‏ ‏.‏ ثُمَّ لَبِثْنَا مَا شَاءَ اللَّهُ فَأُتِيَ بِإِبِلٍ فَأَمَرَ لَنَا بِثَلاَثِ ذَوْدٍ فَلَمَّا انْطَلَقْنَا قَالَ بَعْضُنَا لِبَعْضٍ لاَ يُبَارِكُ اللَّهُ لَنَا أَتَيْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم نَسْتَحْمِلُهُ فَحَلَفَ أَنْ لاَ يَحْمِلَنَا ‏.‏ قَالَ أَبُو مُوسَى فَأَتَيْنَا النَّبِيَّ صلى الله عليه وسلم فَذَكَرْنَا ذَلِكَ لَهُ فَقَالَ ‏"‏ مَا أَنَا حَمَلْتُكُمْ بَلِ اللَّهُ حَمَلَكُمْ إِنِّي وَاللَّهِ لاَ أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ كَفَّرْتُ عَنْ يَمِينِي وَأَتَيْتُ الَّذِي هُوَ خَيْرٌ ‏"‏ ‏.‏