Narrated Fudalah bin 'Ubaid: At the battle of Khaibar I bought a necklace in which there were gold and pearls for twelve dinars. I separated them and found that its worth was more than twelve dinars. So I mentioned that to the Prophet (ﷺ) who said: It must not be sold till the contents are considered separately.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا اللَّيْثُ، عَنْ أَبِي شُجَاعٍ، سَعِيدِ بْنِ يَزِيدَ عَنْ خَالِدِ بْنِ أَبِي عِمْرَانَ، عَنْ حَنَشٍ الصَّنْعَانِيِّ، عَنْ فَضَالَةَ بْنِ عُبَيْدٍ، قَالَ اشْتَرَيْتُ يَوْمَ خَيْبَرَ قِلاَدَةً بِاثْنَىْ عَشَرَ دِينَارًا فِيهَا ذَهَبٌ وَخَرَزٌ فَفَصَّلْتُهَا فَوَجَدْتُ فِيهَا أَكْثَرَ مِنَ اثْنَىْ عَشَرَ دِينَارًا فَذَكَرْتُ ذَلِكَ لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ " لاَ تُبَاعُ حَتَّى تُفَصَّلَ " .
sunnah.com