Q: Is paying off a person’s debt permissible if that debt was contracted for something deemed impermissible in Sharī‘ah?
الجواب حامدا ومصليا ومنه الصدق والصواب
A: In principle, if you gift or lend someone some money that person is free to utilise that money in whichever way he/she feels even if you have given it for a stated purpose. The other person is not required to use the money for the stated purpose only and the usage of that money is the sole
responsibility of the person to whom you have given it. However, if you are aware that the use of the money will be for predominantly impermissible purposes you should not gift or lend to that person so that you are not assisting in sin. If the usage of the money is for predominantly for permissible purposes then you may gift or lend to that person.