[Selling a Commodity for a Cash Price and for a Higher Credit Price]

Answer—and Allah is the granter of success: This issue is a matter of disagreement among the scholars. Some allowed it, and some forbade it. Among those who allowed it are al-Mu’ayyad Billāh (as cited in al-Sharḥ), Abū Ḥanīfah, and al-Shāfiʿī; however, the apparent purport of the evidences supports those who forbid it. It is authentically reported from the Prophet—May Allah bless him and his family and grant them peace—in Majmūʿ al-Imām Zayd ibn ʿAlī (Peace Be Upon Him) that he forbade “two conditions in one sale.” Imām Zayd explained this as when one says: “I sell you this item—if cash, for such-and-such; and if on credit, for such-and-such,” or, “for a term of such-and-such at such-and-such [price], or for a term of such-and-such at such-and-such [price].”
Those who permit it relied on analogy (qiyās). Even if analogy is strong, a textual proof takes precedence over it. Their analogy is: It is authentically established that bringing forward a deferred debt in exchange for remitting part of it is permissible from the Prophet—May Allah bless him and his family and grant them peace. In that case, “time” was exchanged for a portion of the price; so they attached the asked-about case to that, saying: there is no objection to increasing the price because of more time, just as there is no objection to reducing the price for less time. They also adduced the generality of Allah, Exalted is He, saying: “Allah has permitted trade and forbidden usury.” [Al-Baqarah:275]
This analogy may be answered in several ways:
1. It is established in legal theory that the text outweighs analogy when they conflict.
2. It is also established that, when evidences conflict, the side of prohibition is given preference.
3. Even if the form of the analogy appears sound, Allah Most High has prohibited increase, in the verses of ribā, on account of deferment, and He urged reduction, as He said: “And if someone is in hardship, then [let there be] postponement until [a time of] ease; and if you remit it as charity, it is better for you.” [Al-Baqarah:280]
Moreover, when you survey the prohibited sales, you will find that they are, in most cases, directed to the seller’s side—so that the buyer is not wronged; thus the seller is not to be analogized to the buyer in this.
As for their adducing the general verse, that does not settle the dispute.
Yes, those who forbid also cited the report prohibiting the sale of the desperate (bayʿ al-muḍṭarr).
In the marginalia of al-Sharḥ: “ÊNote: In Majmūʿ of ʿAlī Khalīl: If an item has one price when sold in bulk and another price when sold retail, then if the difference between them is slight—within what people commonly overlook—it is permissible to sell the bulk on credit at the retail price; otherwise, it is not permissible.” End
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2