Also, in a previous comment, Reiss frowns upon looking for the Spirit's sanctifying work in our lives as well as the Spirit's testimony that we are children of God as possible grounds of assurance.
However, Martin Luther said (emphasis mine):
Next, the Holy Ghost is sent forth into the hearts of the believers, as here stated, “God sent the Spirit of his Son into your hearts.” This sending is accomplished by the preaching of the Gospel through which the Holy Spirit inspires us with fervor and light, with new judgment, new desires, and new motives. This happy innovation is not a derivative of reason or personal development, but solely the gift and operation of the Holy Ghost.Contextually, Luther is dealing with the doubts of believers. So how does he deal with these doubts? It appears Luther pointed out (at a minimum - I don't see baptism or communion mentioned here for e.g.) the same three grounds which John Frame pointed out (taking his cue from the WCF): the promises of Scripture that if a person trusts Christ alone he is saved; the sanctifying work of the Spirit in the life of the believer; and the witness of the Spirit causing us to cry, "Abba, Father!".
This renewal by the Holy Spirit may not be conspicuous to the world, but it is patent to us by our better judgment, our improved speech, and our unashamed confession of Christ. Formerly we did not confess Christ to be our only merit, as we do now in the light of the Gospel. Why, then, should we feel bad if the world looks upon us as ravagers of religion and insurgents against constituted authority? We confess Christ and our conscience approves of it.
Then, too, we live in the fear of God. If we sin, we sin not on purpose, but unwittingly, and we are sorry for it. Sin sticks in our flesh, and the flesh gets us into sin even after we have been imbued by the Holy Ghost. Outwardly there is no great difference between a Christian and any honest man. The activities of a Christian are not sensational. He performs his duty according to his vocation. He takes good care of his family, and is kind and helpful to others. Such homely, everyday performances are not much admired. But the setting-up exercises of the monks draw great applause. Holy works, you know. Only the acts of a Christian are truly good and acceptable to God, because they are done in faith, with a cheerful heart, out of gratitude to Christ.
We ought to have no misgivings about whether the Holy Ghost dwells in us. We are “the temple of the Holy Ghost” (I Cor. 3:16). When we have a love for the Word of God, and gladly hear, talk, write, and think of Christ, we are to know that this inclination toward Christ is the gift and work of the Holy Ghost. Where you come across contempt for the Word of God, there is the devil. We meet with such contempt for the Word of God mostly among the common people. They act as though the Word of God does not concern them. Wherever you find a love for the Word, thank God for the Holy Spirit who infuses this love into the hearts of men. We never come by this love naturally, neither can it be enforced by laws. It is the gift of the Holy Spirit.
The Roman theologians teach that no man can know for a certainty whether he stands in the favor of God or not. This teaching forms one of the chief articles of their faith. With this teaching they tormented men’s consciences, excommunicated Christ from the Church, and limited the operations of the Holy Ghost.
St. Augustine observed that "every man is certain of his faith, if he has faith." This the Romanists deny. "God forbid," they exclaim piously, "that I should ever be so arrogant as to think that I stand in grace, that I am holy, or that I have the Holy Ghost."
We ought to feel sure that we stand in the grace of God, not in view of our own worthiness, but through the good services of Christ. 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. And although we daily offend God by our sins, yet as often as we sin, God’s mercy bends over us. Therefore sin cannot get us to doubt the grace of God. Our certainty is of Christ, that mighty Hero who overcame the Law, sin, death, and all evils. So long as He sits at the right hand of God to intercede for us, we have nothing to fear from the anger of God.
This inner assurance of the grace of God is accompanied by outward indications such as gladly to hear, preach, praise, and to confess Christ, to do one’s duty in the station in which God has placed us, to aid the needy, and to comfort the sorrowing. These are the affidavits of the Holy Spirit testifying to our favorable standing with God.
If we could be fully persuaded that we are in the good grace of God, that our sins are forgiven, that we have the Spirit of Christ, that we are the beloved children of God, we would be ever so happy and grateful to God. But because we often feel fear and doubt we cannot come to that happy certainty.
Train your conscience to believe that God approves of you. Fight it out with doubt. Gain assurance through the Word of God. Say: “I am all right with God. I have the Holy Ghost. Christ, in whom I do believe, makes me worthy. I gladly hear, read, sing, and write of Him. I would like nothing better than that Christ’s Gospel be known throughout the world and that many, many be brought to faith in Him.”
Verse 6. Crying, Abba, Father.
Paul might have written, “God sent forth the Spirit of his Son into your hearts, calling Abba, Father.” Instead, he wrote, “Crying, Abba, Father.” In the eighth chapter of the Epistle to the Romans the Apostle describes this crying of the Spirit as “groanings which cannot be uttered.” He writes in the 26th verse: “Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered.”
The fact that the Spirit of Christ in our hearts cries unto God and makes intercession for us with groanings should reassure us greatly. However, there are many factors that prevent such full reassurance on our part. We are born in sin. To doubt the good will of God is an inborn suspicion of God with all of us. Besides, the devil, our adversary, goeth about seeking to devour us by roaring: “God is angry at you and is going to destroy you forever.” In all these difficulties we have only one support, the Gospel of Christ. To hold on to it, that is the trick. Christ cannot be perceived with the senses. We cannot see Him. The heart does not feel His helpful presence. Especially in times of trials a Christian feels the power of sin, the infirmity of his flesh, the goading darts of the devil, the agues of death, the scowl and judgment of God. All these things cry out against us. The Law scolds us, sin screams at us, death thunders at us, the devil roars at us. In the midst of the clamor the Spirit of Christ cries in our hearts: “Abba, Father.” And this little cry of the Spirit transcends the hullabaloo of the Law, sin, death, and the devil, and finds a hearing with God.
The Spirit cries in us because of our weakness. Because of our infirmity the Holy Ghost is sent forth into our hearts to pray for us according to the will of God and to assure us of the grace of God.
Let the Law, sin, and the devil cry out against us until their outcry fills heaven and earth. The Spirit of God outcries them all. Our feeble groans, “Abba, Father,” will be heard of God sooner than the combined racket of hell, sin, and the Law.
We do not think of our groanings as a crying. It is so faint we do not know we are groaning. “But he,” says Paul, “that searcheth the hearts knoweth what is the mind of the Spirit” (Romans 8:27). To this Searcher of hearts our feeble groaning, as it seems to us, is a loud shout for help in comparison with which the howls of hell, the din of the devil, the yells of the Law, the shouts of sin are like so many whispers.
In the fourteenth chapter of Exodus the Lord addresses Moses at the Red Sea: “Wherefore criest thou unto me?” Moses had not cried unto the Lord. He trembled so he could hardly talk. His faith was at low ebb. He saw the people of Israel wedged between the Sea and the approaching armies of Pharaoh. How were they to escape? Moses did not know what to say. How then could God say that Moses was crying to Him? God heard the groaning heart of Moses and the groans to Him sounded like loud shouts for help. God is quick to catch the sigh of the heart.
Some have claimed that the saints are without infirmities. But Paul says: “The Spirit helpeth our infirmities, and maketh intercession for us with groanings which cannot be uttered.” We need the help of the Holy Spirit because we are weak and infirm. And the Holy Spirit never disappoints us. Confronted by the armies of Pharaoh, retreat cut off by the waters of the Red Sea, Moses was in a bad spot. He felt himself to blame. The devil accused him: “These people will all perish, for they cannot escape. And you are to blame because you led the people out of Egypt. You started all this.” And then the people started in on Moses. “Because there were no graves in Egypt, hast thou taken us away to die in the wilderness? For it had been better for us to serve the Egyptians, than that we should die in the wilderness” (Ex. 14:11, 12). But the Holy Ghost was in Moses and made intercession for him with unutterable groanings, sighings unto the Lord: “O Lord, at Thy commandment have I led forth this people. So help me now.”
The Spirit intercedes for us not in many words or long prayers, but with groanings, with little sounds like “Abba.” Small as this word is, it says ever so much. It says: “My Father, I am in great trouble and you seem so far away. But I know I am your child, because you are my Father for Christ’s sake. I am loved by you because of the Beloved.” This one little word “Abba” surpasses the eloquence of a Demosthenes and a Cicero.
That said, correct me if I'm wrong, but my impression from modern Lutherans is not only did Luther move on from Luther (e.g. I believe the Galatians commentary was one of Luther's earlier works, c. 1520), but modern Lutherans have moved on from Luther as well.
Of course, I'd hope the main reason they've moved on is because Lutherans believe there's better, more exegetically sound arguments in favor of their current position on the assurance of salvation.
In light of this, see the next post.