Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said that a man of Banu Shamkh bin Fazarah asked (him) about a man who married a woman, then saw her mother, liked her and was attracted to her, so he divorced his wife: may he marry her mother? He said: There is no harm. So the man married her. Sayyiduna Abdullah (may Allah be pleased with him) was in charge of the public treasury (Bayt al-Mal), and he used to sell the inferior items of the treasury, giving much and taking little. Then he came to Madinah and asked the Companions (may Allah be pleased with them), and they said: This woman is not lawful for this man, and silver may only be sold weight for equal weight; otherwise it is not right. When Sayyiduna Abdullah (may Allah be pleased with him) returned, he went to that man but did not find him; his people, however, were there. He said: The fatwa I gave in your case is not right. They said: She has already become pregnant (by him). He said: Even if she has become pregnant. Then he came to the money-changers and said: O company of money-changers! What I used to trade with you is not permissible; selling silver for silver is not permissible except equal for equal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10501
Hadith Gradingمحدثین:اخرجه الفسوي في المعرفه 1/ 88