Luther's Words: Regarding the Holy Spirit and our prayer "Abba Father"

It is a very great comfort that the Spirit of Christ, sent by God into our hearts, cries: "Abba! Father!"  He helps us in our weakness and intercedes for us with sighs too deep for words.  Anyone who truly believed this would not fall away in any affliction.  But many things hinder this faith.  Our heart was born in sin.  Further, we have the innate evil in us that we doubt the favor of God toward us.  We cannot believe with certainty that we are pleasing to Him.  Besides, "our adversary, the devil, as a roaring lion walketh about seeking whom he may devour " (I Peter 5:8) He roars: "God is wrathful with you and will destroy you forever."  We have nothing to strengthen and sustain us except the bare Word which sets Christ forth as the Victor over sin, death, and every evil. But it is effort and labor to cling firmly to this in the midst of trial and conflict.

We do not see Christ, and in the trial our heart does not feel His presence and help.  Then we feel the power of sin, the weakness of the flesh, and our doubt.  We feel the fiery darts of the devil (Eph. 6:16).

           
 Meanwhile, the Holy Spirit is helping us in our weakness and interceding for us.  He merely utters the words of a cry and a sigh, which is "Oh, Father!"  This is indeed a very short Word, but it includes everything.  It is as if one were to say: "Even though I am surrounded by anxieties and seem to be deserted and banished from Thy presence, nevertheless I am a child of God on account of Christ.  I am beloved on account of the Beloved."  Therefore the term "Father", when spoken meaningfully in the heart, is an eloquence that Demosthenes, Cicero, and the most eloquent orators cannot attain.  

 [Lectures on Galatians (1535), LW 26, 380-381, 385]