Selling in installments with an increased price

A: A person is permitted to sell a product, such as foodstuffs or other commodities, and demand payment at a fixed time, even for a higher price because of deferring the payment date. The debtor, on the other hand, should pay off his debt at the fixed time, because of the general meaning of the following Ayah (Qur'anic verse) in which Allah (Exalted be He) says: ...then if one of you entrust the other, let the one who is entrusted discharge his trust (faithfully), and let him be afraid of Allâh, his Lord. It was authentically reported that the Prophet (peace be upon him) said: Whoever takes the money of the people with the intention of repaying it, Allah will repay it on their behalf; and whoever takes it in order to spoil it, then Allah will spoil them. (Part No. 13; Page No. 150) If someone buys a product from a warehouse or a store, for example, and checks it, they are not allowed to sell it in the same place where they bought it even after checking it, because this is not considered a receipt of the sold product. Rather, they should possess it and move it to another place. The evidence is the following Hadith reported by Ahmad (may Allah be merciful to him) on the authority of Hakim ibn Hizam, who said: I said, "O Messenger of Allah! I make some transactions, which of them is lawful for me and which is unlawful?" The Prophet (peace be upon him) replied: "If you buy something, do not sell it until you have it fully in your possession." Moreover, it was related by Ahmad and Abu Dawud on the authority of Zayd ibn Thabit who said: The Prophet (peace be upon him) forbade the selling of goods where they were bought until merchants moved them to their own place. It was also related by Ahmad and Muslim on the authority of Jabir (may Allah be pleased with him) who reported that the Prophet (peace be upon him) said: When you purchase food, do not sell it until you have taken possession of it. (Part No. 13; Page No. 151) In another narration, Muslim reported that the Prophet (peace be upon him) said: Whoever buys food should not sell it, until they have weighed it (and then taken possession of it). May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.