In Islam, usury is forbidden. It’s an unfair deal to exploit people in need and lend them money on the condition that s/she will pay back double or ten doubles.
But what if usuary was not about money?
I’ve just read this quote by Shams Tabrizi;
“Usuary is permissible in love. So, when one gives you some love, give it back double.”
Wishing you all the best,