In his exposition of 1 Peter 2:12, Martin Luther takes issue with Christians who thought that after absolution or baptism they could take it easy and relax . . .
"If you want to go to confession and be absolved, you must act like a soldier who takes the lead in battle when this is really important and the war begins. Now one must fight in earnest, just as though previously this had been sport. Now one must draw the sword and lay about with a vengeance. But there must be vigilance as long as the battle lasts.
"Thus even if you are baptized, you must realize that you are never safe from the devil and from sin. Indeed, you must remember that now you will have no peace. Thus the Christian life is nothing but a battle and a camp, as Scripture says.
"Therefore our Lord God is also Dominus Sabaoth (Ps. 24:10), that is, a Lord of hosts. Likewise, Dominus potens in proelio, “the Lord mighty in battle” (Ps. 24:8). He shows His might by letting His people wage war constantly and by letting them take the lead where the trumpets always sound. They must constantly remember to exclaim: “To the defense here! To the defense there! Thrust here! Strike there!” Thus this is an everlasting struggle, and you must do all you can to strike the devil down with the Word of God. Here one must always resist, call upon God, and despair of all human powers." (AE 30:71-72)