We were along with Fadala b. Ubaid (Allah be pleased with him) in an expedition. There fell to my and my friend's lot a necklace made of gold, silver and jewels. I decided to buy that. I asked Fadala b. 'Ubaid, whereupon he said: Separate its gold and place it in one pan (of the balance) and place your gold in the other pan, and do not receive but equal for equal, for I heard Messenger of Allah ﷺ as saying: He who believes in Allah and the Hereafter should not take but equal for equal.  

انْزِعْ ذَهَبَهَا فَاجْعَلْهُ فِي كِفَّةٍ وَاجْعَلْ ذَهَبَكَ فِي كِفَّةٍ ثُمَّ لاَ تَأْخُذَنَّ إِلاَّ مِثْلاً بِمِثْلٍ فَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلاَ يَأْخُذَنَّ إِلاَّ مِثْلاً بِمِثْلٍ  

[Machine] Necklaces adorned with gold, silver, and jewels flew towards me and my companions. I desired to purchase them, so I asked Fadalah ibn 'Ubayd. He advised me to take off the gold and place it on one hand, while placing my own gold on the other hand. Then he told me to only take the equivalent in exchange. For I have heard the Messenger of Allah ﷺ say, "Whoever believes in Allah and the Last Day should only take the equivalent in exchange."  

فَطَارَتْ لِي وَلِأَصْحَابِي قَلَائِدُ فِيهَا ذَهَبٌ وَوَرِقٌ وَجَوْهَرٌ فَأَرَدْتُ أَنْ أَشْتَرِيَهَا فَسَأَلْتُ فَضَالَةَ بْنَ عُبَيْدٍ فَقَالَ انْزِعْ ذَهَبَهَا فَاجْعَلْهُ فِي كِفَّةٍ وَاجْعَلْ ذَهَبَكَ فِي كِفَّةٍ ثُمَّ لَا تَأْخُذَنَّ إِلَّا مِثْلًا بِمِثْلٍ؛ فَإِنِّي سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ مَنْ كَانَ يُؤْمِنُ بِاللهِ وَالْيَوْمِ الْآخِرِ فَلَا يَأْخُذَنَّ إِلَّا مِثْلًا بِمِثْلٍ