Sahih Muslim , Book 10, Hadith 3863 (USC-MSA) ⓘ
Fadala b. Ubaid al-Ansari reported: A necklace having gold and gems in it was brought to Allah's Messenger in Khaibar and it was one of the spoils of war and was put to sale. Allah's Messenger said: The gold used in it should be separated, and then Allah's Messenger further said: (Sell) gold for gold with equal weight.
حَدَّثَنِي أَبُو الطَّاهِرِ، أَحْمَدُ بْنُ عَمْرِو بْنِ سَرْحٍ أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي أَبُو هَانِئٍ الْخَوْلاَنِيُّ أَنَّهُ سَمِعَ عُلَىَّ بْنَ رَبَاحٍ اللَّخْمِيَّ، يَقُولُ سَمِعْتُ فَضَالَةَ بْنَ عُبَيْدٍ الأَنْصَارِيَّ، يَقُولُ أُتِيَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَهُوَ بِخَيْبَرَ بِقِلاَدَةٍ فِيهَا خَرَزٌ وَذَهَبٌ وَهِيَ مِنَ الْمَغَانِمِ تُبَاعُ فَأَمَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِالذَّهَبِ الَّذِي فِي الْقِلاَدَةِ فَنُزِعَ وَحْدَهُ ثُمَّ قَالَ لَهُمْ رَسُولُ اللَّهِ صلى الله عليه وسلم " الذَّهَبُ بِالذَّهَبِ وَزْنًا بِوَزْنٍ " .
also referenced under: Book 22, Hadith 114 (In-Book) & Hadith 1591 (Reference)