The first thesis of Martin Luther’s 95 theses is as follows: “When our Lord and Master Jesus Christ said, ‘Repent’ [Matt. 4:17], he willed the entire life of believers to be one of repentance.”
An important distinction that needs to be made regarding repentance is that it is not a work that we do, but a work that is done upon us by God. As we hear God’s Law (His commands and demands) in Holy Scripture, the Holy Spirit works repentance in us and upon us. Confronted with our sins and being brought to the awareness that we rightly stand under God’s just judgment, we are grieved for what we have done and appeal to God for mercy for the sake of Jesus’ blood shed for us. Left to ourselves, we would forget all about God’s demand that we be holy and perfectly obedient to His Law, and thus we would reach the false conclusion that we are living a pretty good life and that God knows we are trying our best.
Apart from the Holy Spirit working through God’s Law to show us our sin and lostness, we would face the peril of unrepentance – which is always the danger when we think that we are acceptable to God in and of ourselves. Repentance is, therefore, a gift which the Spirit works in us that we might gladly hear the good news (Gospel) that Christ Jesus has died in our place and answered for our sins. The Holy Spirit also works in us and upon us through the word of the Gospel (God’s gracious promises), which creates in us the faith to believe that all of our sins have been forgiven for the sake of Jesus’ sacrifice for us upon the Cross.
If we are saved on the Last Day, it is because the Holy Spirit has worked through God’s Word of both Law and Gospel so that we may believe in the Savior who has merited our forgiveness and salvation upon his Cross. Thus, the call to repentance is to receive in ourselves the working of the Spirit through the Holy Scriptures. You received the Spirit when you were baptized, pray that He may accomplish in you the gifts of repentance and faith that lead to eternal life, for Jesus’ sake.