Muwatta Imam Malik Book of Business Transactions, Hadith 54

Yahya related to me from Malik that he had heard that Muhammad Sirin used to say, "Do not sell grain on the ears until it is white."
Malik said, "If someone buys food for a known price to be delivered at a stated date, and when the date comes, the one who owes the food says, 'I do not have any food, sell me the food which I owe you with delayed terms.' The owner of the food says, 'This is not good, because the Messenger of Allah ﷺ forbade selling food until the deal was completed.' The one who owes the food says to his creditor, 'Sell me any kind of food on delayed terms until I discharge the debt to you.' This is not good because he gives him food and then he returns it to him. The gold which he gave him becomes the price of that which is his right against him and the food which he gave him becomes what clears what is between them. If they do that, it becomes the sale of food before the deal is complete."
Malik spoke about a man who was owed food which he had purchased from a man and this man was owed the like of that food by another man. The one who owed the food said to his creditor, "I will refer you to my debtor who owes me the same amount of food as I owe you, so that you may obtain the food which I owe you ."
Malik said, "If the man who had to deliver the food, had gone out, and bought the food to pay off his creditor, that is not good. That is selling food before taking possession of it. If the food is an advance which falls due at that particular time, there is no harm in paying off his creditor with it because that is nota sale. It is not halal to sell food before receiving it in full since the Messenger of Allah ﷺ forbade that. However, the people of knowledge agree that there is no harm in partnership, transfer of responsibility and revocation in sales of food and other goods."
Malik said, "That is because the people of knowledge consider it as a favour rendered. They do not consider it as a sale. It is like a man lending light dirhams. He is then paid back in dirhams of full weight, and so gets back more than he lent. That is halal for him and permitted. Had a man bought defective dirhams from him as being the full weight, that would not be halal. Had it been stipulated to him that he lend full weight in dirhams, and then he gave faulty ones, that would not be halal for him."

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ مُحَمَّدَ بْنَ سِيرِينَ، كَانَ يَقُولُ لاَ تَبِيعُوا الْحَبَّ فِي سُنْبُلِهِ حَتَّى يَبْيَضَّ . قَالَ مَالِكٌ مَنِ اشْتَرَى طَعَامًا بِسِعْرٍ مَعْلُومٍ إِلَى أَجَلٍ مُسَمًّى فَلَمَّا حَلَّ الأَجَلُ قَالَ الَّذِي عَلَيْهِ الطَّعَامُ لِصَاحِبِهِ لَيْسَ عِنْدِي طَعَامٌ فَبِعْنِي الطَّعَامَ الَّذِي لَكَ عَلَىَّ إِلَى أَجَلٍ . فَيَقُولُ صَاحِبُ الطَّعَامِ هَذَا لاَ يَصْلُحُ لأَنَّهُ قَدْ نَهَى رَسُولُ اللَّهِ ﷺ عَنْ بَيْعِ الطَّعَامِ حَتَّى يُسْتَوْفَى . فَيَقُولُ الَّذِي عَلَيْهِ الطَّعَامُ لِغَرِيمِهِ فَبِعْنِي طَعَامًا إِلَى أَجَلٍ حَتَّى أَقْضِيَكَهُ . فَهَذَا لاَ يَصْلُحُ لأَنَّهُ إِنَّمَا يُعْطِيهِ طَعَامًا ثُمَّ يَرُدُّهُ إِلَيْهِ . فَيَصِيرُ الذَّهَبُ الَّذِي أَعْطَاهُ ثَمَنَ الَّذِي كَانَ لَهُ عَلَيْهِ وَيَصِيرُ الطَّعَامُ الَّذِي أَعْطَاهُ مُحَلَّلاً فِيمَا بَيْنَهُمَا وَيَكُونُ ذَلِكَ إِذَا فَعَلاَهُ بَيْعَ الطَّعَامِ قَبْلَ أَنْ يُسْتَوْفَى . قَالَ مَالِكٌ فِي رَجُلٍ لَهُ عَلَى رَجُلٍ طَعَامٌ ابْتَاعَهُ مِنْهُ وَلِغَرِيمِهِ عَلَى رَجُلٍ طَعَامٌ مِثْلُ ذَلِكَ الطَّعَامِ فَقَالَ الَّذِي عَلَيْهِ الطَّعَامُ لِغَرِيمِهِ أُحِيلُكَ عَلَى غَرِيمٍ لِي عَلَيْهِ مِثْلُ الطَّعَامِ الَّذِي لَكَ عَلَىَّ بِطَعَامِكَ الَّذِي لَكَ عَلَىَّ . قَالَ مَالِكٌ إِنْ كَانَ الَّذِي عَلَيْهِ الطَّعَامُ إِنَّمَا هُوَ طَعَامٌ ابْتَاعَهُ فَأَرَادَ أَنْ يُحِيلَ غَرِيمَهُ بِطَعَامٍ ابْتَاعَهُ فَإِنَّ ذَلِكَ لاَ يَصْلُحُ وَذَلِكَ بَيْعُ الطَّعَامِ قَبْلَ أَنْ يُسْتَوْفَى فَإِنْ كَانَ الطَّعَامُ سَلَفًا حَالاًّ فَلاَ بَأْسَ أَنْ يُحِيلَ بِهِ غَرِيمَهُ لأَنَّ ذَلِكَ لَيْسَ بِبَيْعٍ وَلاَ يَحِلُّ بَيْعُ الطَّعَامِ قَبْلَ أَنْ يُسْتَوْفَى لِنَهْىِ رَسُولِ اللَّهِ ﷺ عَنْ ذَلِكَ غَيْرَ أَنَّ أَهْلَ الْعِلْمِ قَدِ اجْتَمَعُوا عَلَى أَنَّهُ لاَ بَأْسَ بِالشِّرْكِ وَالتَّوْلِيَةِ وَالإِقَالَةِ فِي الطَّعَامِ وَغَيْرِهِ . قَالَ مَالِكٌ وَذَلِكَ أَنَّ أَهْلَ الْعِلْمِ أَنْزَلُوهُ عَلَى وَجْهِ الْمَعْرُوفِ وَلَمْ يُنْزِلُوهُ عَلَى وَجْهِ الْبَيْعِ وَذَلِكَ مِثْلُ الرَّجُلِ يُسَلِّفُ الدَّرَاهِمَ النُّقَّصَ فَيُقْضَى دَرَاهِمَ وَازِنَةً فِيهَا فَضْلٌ فَيَحِلُّ لَهُ ذَلِكَ وَيَجُوزُ وَلَوِ اشْتَرَى مِنْهُ دَرَاهِمَ نُقَّصًا بِوَازِنَةٍ لَمْ يَحِلَّ ذَلِكَ وَلَوِ اشْتَرَطَ عَلَيْهِ حِينَ أَسْلَفَهُ وَازِنَةً وَإِنَّمَا أَعْطَاهُ نُقَّصًا لَمْ يَحِلَّ لَهُ ذَلِكَ . قَالَ مَالِكٌ وَمِمَّا يُشْبِهُ ذَلِكَ أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنْ بَيْعِ الْمُزَابَنَةِ وَأَرْخَصَ فِي بَيْعِ الْعَرَايَا بِخَرْصِهَا مِنَ التَّمْرِ وَإِنَّمَا فُرِقَ بَيْنَ ذَلِكَ أَنَّ بَيْعَ الْمُزَابَنَةِ بَيْعٌ عَلَى وَجْهِ الْمُكَايَسَةِ وَالتِّجَارَةِ وَأَنَّ بَيْعَ الْعَرَايَا عَلَى وَجْهِ الْمَعْرُوفِ لاَ مُكَايَسَةَ فِيهِ . قَالَ مَالِكٌ وَلاَ يَنْبَغِي أَنْ يَشْتَرِيَ رَجُلٌ طَعَامًا بِرُبُعٍ أَوْ ثُلُثٍ أَوْ كِسْرٍ مِنْ دِرْهَمٍ عَلَى أَنْ يُعْطَى بِذَلِكَ طَعَامًا إِلَى أَجَلٍ وَلاَ بَأْسَ أَنْ يَبْتَاعَ الرَّجُلُ طَعَامًا بِكِسْرٍ مِنْ دِرْهَمٍ إِلَى أَجَلٍ ثُمَّ يُعْطَى دِرْهَمًا وَيَأْخُذُ بِمَا بَقِيَ لَهُ مِنْ دِرْهَمِهِ سِلْعَةً مِنَ السِّلَعِ لأَنَّهُ أَعْطَى الْكِسْرَ الَّذِي عَلَيْهِ فِضَّةً وَأَخَذَ بِبَقِيَّةِ دِرْهَمِهِ سِلْعَةً فَهَذَا لاَ بَأْسَ بِهِ . قَالَ مَالِكٌ وَلاَ بَأْسَ أَنْ يَضَعَ الرَّجُلُ عِنْدَ الرَّجُلِ دِرْهَمًا ثُمَّ يَأْخُذُ مِنْهُ بِرُبُعٍ أَوْ بِثُلُثٍ أَوْ بِكِسْرٍ مَعْلُومٍ سِلْعَةً مَعْلُومَةً فَإِذَا لَمْ يَكُنْ فِي ذَلِكَ سِعْرٌ مَعْلُومٌ وَقَالَ الرَّجُلُ آخُذُ مِنْكَ بِسِعْرِ كُلِّ يَوْمٍ فَهَذَا لاَ يَحِلُّ لأَنَّهُ غَرَرٌ يَقِلُّ مَرَّةً وَيَكْثُرُ مَرَّةً وَلَمْ يَفْتَرِقَا عَلَى بَيْعٍ مَعْلُومٍ . قَالَ مَالِكٌ وَمَنْ بَاعَ طَعَامًا جِزَافًا وَلَمْ يَسْتَثْنِ مِنْهُ شَيْئًا ثُمَّ بَدَا لَهُ أَنْ يَشْتَرِيَ مِنْهُ شَيْئًا فَإِنَّهُ لاَ يَصْلُحُ لَهُ أَنْ يَشْتَرِيَ مِنْهُ شَيْئًا إِلاَّ مَا كَانَ يَجُوزُ لَهُ أَنْ يَسْتَثْنِيَ مِنْهُ وَذَلِكَ الثُّلُثُ فَمَا دُونَهُ فَإِنْ زَادَ عَلَى الثُّلُثِ صَارَ ذَلِكَ إِلَى الْمُزَابَنَةِ وَإِلَى مَا يُكْرَهُ فَلاَ يَنْبَغِي لَهُ أَنْ يَشْتَرِيَ مِنْهُ شَيْئًا إِلاَّ مَا كَانَ يَجُوزُ لَهُ أَنْ يَسْتَثْنِيَ مِنْهُ وَلاَ يَجُوزُ لَهُ أَنْ يَسْتَثْنِيَ مِنْهُ إِلاَّ الثُّلُثَ فَمَا دُونَهُ وَهَذَا الأَمْرُ الَّذِي لاَ اخْتِلاَفَ فِيهِ عِنْدَنَا .