(51) باب أَخْذِ الْوَرِقِ مِنَ الذَّهَبِ وَالذَّهَبِ مِنَ الْوَرِقِ وَذِكْرِ اخْتِلاَفِ أَلْفَاظِ النَّاقِلِينَ لِخَبَرِ ابْنِ عُمَرَ فِيهِ
It was narrated that Ibn 'Umar said:
"I used to sell gold for silver, or silver for gold. I came to the Messenger of Allah and told him about that, and he said: 'If you make a deal with your companion, d o not leave him when there is still any ambiguity (in the deal) between you."'
Reference: Sunan an-Nasa'i 4583
In-book reference: Book 44, Hadith 135
English translation: Vol. 5, Book 44, Hadith 4587