Have Faith in God: Laying Ahold of His Promises in Prayer

In Mark 11:22 and Jesus answered, saying to them, "Have faith in God." This is a command, isn't it? He does not say, ask for faith. He does not say wait for faith. He does not say, "Well, maybe in a year or two some faith will show up." But he says: You do this. You believe God. Have faith on who? On God; it does not say have faith in your feelings of faith.