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Baptism is not simply plain water. Instead it is water used according to God’s command and connected with God’s word, as our Lord Jesus Christ says in Matthew 28:19, “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.”
Baptism brings about forgiveness of sins, redeems from death and the devil, and gives eternal salvation to all who believe it, as the words and promise of God declare in Mark 16:16, where our Lord Jesus Christ says, “The one who believes and is baptized will be saved; but the one who does not believe will be condemned.”
Clearly the water does not do these great things, but the word of God, which is with and alongside the water, and faith, which trusts this word of God in the water. For without the word of God the water is plain water and not a baptism, but with the word of God it is a baptism, that is, a grace-filled water of life and a “bath of the new birth in the Holy Spirit,” as St. paul says to Titus in chapter 3, “through the water of rebirth and renewal by the Holy Spirit. This Spirit he poured out on us richly through Jesus Christ our Savior, so that, having been justified by his grace, we might become heirs according to the hope of eternal life. This is most certainly true.”
The significance of baptism with such water is that the old person in us with all sins and evil desires is to be drowned and die through daily sorrow for sin and through repentance, and on the other hand that daily a new person is to come forth and rise up to live before God in righteousness and purity forever.