ما المقصود بالنهي عن بيعتين في بيعة؟

Regarding the prohibition of two sales in one transaction, it is authentically reported that the Messenger of Allah (peace and blessings be upon him) forbade it. Various narrations have been reported in interpreting this prohibition. Among them is what Malik, Shafi'i, and Ahmad interpreted it as: selling a commodity for a cash price and a higher price for deferred payment without specifying, or that the buyer stipulates selling one commodity for a certain price and buying another from him for a different price. Ibn al-Qayyim interpreted it as selling a commodity for a deferred price on condition that the seller buys it back for a lower cash price. There is another interpretation that it is stipulating one sale within another sale, such as selling something on condition that the other party buys something else from him, or combining a sale with an exchange. Al-Khattabi interpreted it as a usurious sale where the second sale enters into the first sale.