Faith is acting upon what you feel God calling you to do with no guarantees as to whether it will work or not.
Walking into the Red Sea. Hoping, believing the waters will part. An act of sheerest insanity. An acting upon what you, or one in whom you put your absolute faith, is absolutely sure is the clearest word of God.
It comes down to that with tithing, for instance. Christ says, Give and you shall receive, full measure, pressed down, flowing over. Will we? We have to try it to see. What’s more, give without telling anyone. Cut off any possibility of any reward except from God.