قَالَ مَالِك : إِذَا اصْطَرَفَ الرَّجُلُ دَرَاهِمَ بِدَنَانِيرَ ثُمَّ وَجَدَ فِيهَا دِرْهَمًا زَائِفًا فَأَرَادَ رَدَّهُ، انْتَقَضَ صَرْفُ الدِّينَارِ وَرَدَّ إِلَيْهِ وَرِقَهُ وَأَخَذَ إِلَيْهِ دِينَارَهُ . وَتَفْسِيرُ مَا كُرِهَ مِنْ ذَلِكَ : أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ، قَالَ : " الذَّهَبُ بِالْوَرِقِ رِبًا إِلَّا هَاءَ وَهَاءَ " . وَقَالَ عُمَرُ بْنُ الْخَطَّابِ : وَإِنِ اسْتَنْظَرَكَ إِلَى أَنْ يَلِجَ بَيْتَهُ فَلَا تُنْظِرْهُ، وَهُوَ إِذَا رَدَّ عَلَيْهِ دِرْهَمًا مِنْ صَرْفٍ بَعْدَ أَنْ يُفَارِقَهُ كَانَ بِمَنْزِلَةِ الدَّيْنِ أَوِ الشَّيْءِ الْمُتَأَخِّرِ . فَلِذَلِكَ كُرِهَ ذَلِكَ، وَانْتَقَضَ الصَّرْفُ، وَإِنَّمَا أَرَادَ عُمَرُ بْنُ الْخَطَّابِ أَنْ لَا يُبَاعَ الذَّهَبُ وَالْوَرِقُ وَالطَّعَامُ كُلُّهُ عَاجِلًا بِآجِلٍ، فَإِنَّهُ لَا يَنْبَغِي أَنْ يَكُونَ فِي شَيْءٍ مِنْ ذَلِكَ تَأْخِيرٌ وَلَا نَظِرَةٌ، وَإِنْ كَانَ مِنْ صِنْفٍ وَاحِدٍ أَوْ كَانَ مُخْتَلِفَةً أَصْنَافُهُ
Imam Malik, may Allah have mercy on him, said that if a person took rupees in exchange for gold coins, and then one rupee turned out to be counterfeit, and now he wishes to return it, then he should return all the gold coins, and all the rupees should be given back to him, because the Messenger of Allah, peace and blessings be upon him, said: "There is riba in exchanging gold for silver except when it is hand to hand." And Sayyiduna Umar, may Allah be pleased with him, said: If he asks you for time to go home, do not grant him respite; if you return one rupee to him and separate from him, it will become like a debt or a term, and for this reason, it is disliked. One should annul such a sale oneself, so that on one side it is cash and on the other side it is a promise, whether it is of one kind or of several kinds.