Is it permissible to put money into the Canadian RESP system, to which the bank adds interest, in order to benefit from the government grant, while getting rid of the usurious interest? What is the ruling on the mother signing this contract, and does the sin fall solely on the husband if he approves of the matter?

Depositing money in a usurious savings or investment account is religiously forbidden. It is a usurious loan by consensus, due to the severe warnings associated with it. The Messenger of Allah, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses, saying: "They are all equal." Furthermore, receiving a grant from the state does not make it permissible to fall into usury, and it is not permissible to participate in such a system.