I made a deal with a contractor to build a house based on installments. We agreed that I would pay him an amount of money as a deposit, and then I would pay the rest of the money in installments after he completes the building. The contractor told me that he would sell the checks that he receives from me to the bank. I will not pay any additional amount of money than what we agreed upon whether he sells the checks to the bank or whether I pay the installments every month. I know that selling checks to the bank in return for a lesser amount of money than the real amount is considered Riba (usury). (As for me), am I helping him to deal in Riba or not?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is alright to go on with this deal, but you should advise the contractor and tell him that what he will do is plain Riba and point out to him that Riba is prohibited as it is considered fighting Allaah The Almighty and it brings about His curse. You should mention to him the verses and Hadeeths (narrations)  that indicate this. Allaah The Almighty Says (what means): {Allaah destroys interest and gives increase for charities.} [Quran 2:276]

The Prophet, sallallaahu ‘alayhi wa sallam, cursed the one who took or gave Riba. [Al-Bukhari] It was narrated that the Prophet, sallallaahu ‘alayhi wa sallam, cursed the consumer of Riba and its payer, and the one who records it, and the two witnesses, and he said: “They are all equal (in sin)." [Muslim]

Allaah Knows best.