What is the ruling on dealing with banks that offer loans accompanied by a Shar'i document (legal certificate) attesting to their permissibility and conformity with Islamic Law?

The permissible loan is a benevolent loan (Qard Hasan) in which no increase is stipulated upon its repayment. As for a loan in which an increase is stipulated, it is an interest-bearing loan (riba) and is impermissible to take. Ibn al-Mundhir said: "They have unanimously agreed that if the lender stipulates an increase or a gift from the borrower, and lends on that condition, then taking the increase on that basis is usury (riba)." As for murabaha contracts conducted by some banks, their permissibility is subject to certain conditions.