It is said that actions speak louder than words. Is the opposite true...i.e., that words speak louder than actions? Your friend requests a loan of $100. to be paid back in a month. The month comes and goes and no repayment. You, ask your friend for repayment, but (s)he states that (s)he doesn't have it. Your trust in that person is broken - - temporarily or forever. That depends on what further statements are made to the agreement of the lender.
The "action" is that repayment was NOT made. The words then become key. Words that would convey and request understanding, a honest explanation as to the circumstances, a different payback date, an installment plan, etc. If the lender (the one doing the lending) hears that the person doing the "borrowing" is sincere, apologetic, contrite, there is an opportunity for trust to be re-established.
Whether you are in an established relationship, or dating, trust plays a HUGE role of determining whether this is a person worthy of your time and commitment. This is extremely important. You would want to know whether the individual you are dealing with share similar values as you do. I'm saying that if you lend a boyfriend or girlfriend $100.00 and he/she doesn't repay when stated, to me, that's a red flag, and it should be for you too. One red flag. Are there others?
What builds trust is having a very good feeling about that person. Something I, myself, state to others, when necessary, is, "My word is my bond." I don't have to sign on the dotted line. I am saying, "you can trust me." Whatever, I agree to will absolutely occur. Look for people in your lives that you can absolutely trust. It will become quite apparent whether that person, or any person, is just that--- someone you can trust.
Take a listen to Dionne Warwick's, "Promises, Promises" on You Tube. An oldie, but goodie.