(90) بَابُ أَدَبِ الْخَادِمِ
Yazid ibn 'Abdullah said, "'Abdullah ibn 'Umar sent a slave ofhis with some gold - or silver - and he changed it and deferredthe exchange (i.e. he changed gold into silver or vice versa and did nottake the money straightaway. This is haram.) Then he went back to Ibn 'Umarwho gave him a painful beating. He said, 'Go and take what is mine anddo not exchange it!'"
Reference: Al-Adab Al-Mufrad 170
In-book reference: Book 9, Hadith 15
English translation: Book 9, Hadith 170