Is one who works on mortgaging a fishing vessel in a concerned ministry, on behalf of its owner, after the owner of the vessel has agreed with a bank on an interest-based loan, sinful, and does the Hadith: "Allah has cursed the one who consumes Riba, the one who pays it, the one who writes it down, and the two who witness it" apply to him?

Borrowing from a bank with interest is forbidden usury. It is not permissible except in cases of dire necessity that lead to ruin or unbearable hardship. It is not permissible for the questioner's brother to carry out procedures for mortgaging the boat in the bank's name on behalf of the boat owner, as this constitutes aiding in what is forbidden.