He asked my help because I have a land but I am not willing to sell it. Can I sign him a false commitment for him to save his mother’s life?

It is not permissible for him to borrow with interest and hence it is not permissible for you to help him by any means.

A colleague wants borrow money with interest.He will use the money for a medical purpose. But this bank only grants the money for the client who will use it to buy a land after a delivery of selling commitment from a third party.