"Comprehend the difference, then, that Baptism is quite another thing than all other water; not on account of the natural quality but because something more noble is here added; for God Himself stakes His honor, His power and might on it. Therefore it is not only natural water, but a divine, heavenly, holy, and blessed water, and in whatever other terms we can praise it,-all on account of the Word, which is a heavenly, holy Word, that no one can sufficiently extol, for it has, and is able to do, all that God is and can do [since it has all the virtue and power of God comprised in it]. Hence also it derives its essence as a Sacrament, as St. Augustine also taught: Accedat verbum ad elementum et fit sacramentum. That is, when the Word is joined to the element or natural substance, it becomes a Sacrament, that is, a holy and divine matter and sign." - Martin Luther's Large Catechism, Section IV, 17-18
"Thus, and much more even, you must honor Baptism and esteem it glorious on account of the Word, since He Himself has honored it both by words and deeds; moreover, confirmed it with miracles from heaven. For do you think it was a jest that, when Christ was baptized, the heavens were opened and the Holy Ghost descended visibly, and everything was divine glory and majesty?" ibid. 21
"In the second place, since we know now what Baptism is, and how it is to be regarded, we must also learn why and for what purpose it is instituted; that is, what it profits, gives, and works. And this also we cannot discern better than from the words of Christ above quoted: He that believeth and is baptized shall be saved. Therefore state it most simply thus, that the power, work, profit, fruit, and end of Baptism is this, namely, to save. For no one is baptized in order that he may become a prince, but, as the words declare, that he be saved. But to be saved, we know, is nothing else than to be delivered from sin, death, and the devil, and to enter into the kingdom of Christ, and to live with Him forever.
Here you see again how highly and precious we should esteem Baptism, because in it we obtain such an unspeakable treasure, which also indicates sufficiently that it cannot be ordinary mere water. For mere water could not do such a thing, but the Word does it, and (as said above) the fact that the name of God is comprehended therein. But where the name of God is, there must be also life and salvation, that it may indeed be called a divine, blessed, fruitful, and gracious water; for by the Word such power is imparted to Baptism that it is a laver of regeneration, as St. Paul also calls it, Titus 3:5." - ibid. 23-27
-CryptoLutheran