On the other hand, says Zechariah, this poor and humble King will have a power greater than that of all emperors and kings who have ever lived on earth, great as their power may have been. For He is called Justus et Salvator. Not a rich, noble and mighty king before the world, but the Just One and Savior, who shall bring with Him righteousness and salvation, attack sin and death, be the enemy of sin and destroyer of death; for He comes for the purpose of saving from sin and eternal death all who believe in Him, receive Him as their king, and are not offended at the poor borrowed ass. Those who receive Him in faith and find their consolation in Him, receive forgiveness of sins, and shall not die, but live forever. And though after their bodies they must die and be buried, it shall be to them, and be called by them, not death, but only a sleep.
This the prophet would teach us of this King, when he gives Him these two glorious, nay divine, titles and names, calling Him the Just One and Savior, who shall rob death of his power, hell of its destruction, tread the devil under His feet, and thus deliver us who believe in Him from sin and death, and introduce us to the society of angels, where there is eternal life and salvation. He leaves other kings in possession of their external government, authority, pomp, castles, houses, money and goods, allows them also to eat, drink, clothe themselves, and build in a more costly manner than other people; but this art they do not understand, this work they cannot do, which this poor and humble King, Christ, understands and does. (Luther’s House Postil, Sermon for the 1st Sunday in Advent, Volume 1, p. 19)