But when you give to the needy, do not let your left hand know what your right hand is doing, so that your giving may be in secret. Then your Father, who sees what is done in secret, will reward you.
Not letting your left hand see what your right hand is doing is referring to not being boastful of your good deeds. It is important for our good deeds to be done in purity versus vanity, nothing done in vanity shall prosper and or be blessed. It is very easy to give with mixed motives while doing something for someone, or giving back, but we should avoid all scheming when giving back.
To make sure that we give back from a pure and genuine place, practice humility.