In which cases is usury permissible?

It is permissible to engage in usury for someone who is on the verge of perishing or is in severe distress for which they find no solution except through it, due to the Almighty's saying: "And He has already explained to you what He has forbidden to you, except for that to which you are compelled," and His saying: "But whoever is compelled, neither desiring [it] nor transgressing [its limit], there is no sin upon him." Necessity is estimated by its extent. If the necessity ceases or an alternative is found, usury reverts to its original status of prohibition. Usurious transactions in trade, loans, and deposits with interest are not considered a matter of necessity.