[Increasing a Commodity’s Price on Account of Credit]

Answer—and Allah is the granter of success: The scholars of the madhhab—foremost among them al-Hādī (Peace Be Upon Him)—have forbidden such a sale and prohibited that increase, counting it among the usury that is forbidden and against which there is severe threat for the one who practices it or consumes it.
This madhhab is nearer to precaution and farther from doubt and misgivings. In the hadith: “Leave what makes you doubt for what does not make you doubt,” and in the report: “The believers pause at doubtful matters.”
Some of the Imams of Ahl al-Bayt (Peace Be Upon Them) permitted such a sale. Their proof is analogy with what is soundly established from the Prophet—May Allah bless him and his family and grant them peace—of allowing early settlement of a deferred debt in exchange for remitting part of it; they said: since the Prophet—May Allah bless him and his family and grant them peace—permitted remitting part of the price in exchange for time in that case, it follows that time may be counter-valued by price in sales and purchases. This issue is not decisively settled, as evidenced by the occurrence of disagreement among the Imams of Ahl al-Bayt (Peace Be Upon Them) over its permissibility.
Nevertheless, the first madhhab is safer, nearer to precaution, and farther from doubtful matters.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2