Is it permissible to take out an interest-bearing loan to complete the wedding preparations, knowing that this is the only available solution to proceed with the marriage, especially since the father's pension will stop after the marriage contract?

Borrowing with usury is one of the gravest sins and destructive acts, and it is not permissible except in cases of extreme necessity, such as fear of perishing. Completing a marriage or purchasing its requirements does not fall under this necessity. It is not permissible to borrow with usury for the purpose mentioned. If it is possible to borrow without usury, then that is permissible; otherwise, one should be patient and seek help from Allah. For Allah guarantees provision for those who rely upon Him, as stated in the two verses: "And let those who find not [the means for] marriage abstain [from sexual relations] until Allah enriches them from His bounty." (An-Nur: 33) and "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect. And whoever relies upon Allah - then He is sufficient for him." (At-Talaq: 2-3).