Note the order of events. First you are made an adopted son. Then the Spirit of God comes into your heart and says "Abba" Father through you in prayer. Automatically the word comes out. You just know so much that you are a son that your tongue admits to it immediately (4:6).

Macarthur tells us that Abba is “an Aramaic term of endearment, used by young children to speak to their fathers; the equivalent of the word Daddy.”

Luther, denying those who try to quash a man’s certainty of his salvation, says, “As certain as we are that Christ pleases God, so sure ought we to be that we also please God, because Christ is in us.”

He argues in another place, “If our [Roman] opponents are so uncertain about their status with God, and even go so far as to say that the conscience ought to be kept in a state of doubt, why is it that they persecute us as vile heretics? When it comes to persecuting us, they do not seem to be in doubt and uncertainty one minute.”

From a slave bound to this world and with no relationship to the true God, to a son calling out “Daddy” to a personal Friend in Heaven, to an heir of the promise of the Spirit and of eternal life.