I have noted a tendency among some Christians to find some inconsistency between moral effort and justification by grace through faith. . . .

So Scripture commands us to yield our lives to God (Rom. 6:19; Phil. 3:13-14; Col. 3:10; Heb. 12:1), to strive for holiness (Rom. 8:13; 2 Cor. 7:1; 1 Thess. 4:3; Heb. 12:14; 1 Peter 1:15; 2 Peter 1:5; 1 John 3:3), to don the whole armor of God (Eph. 6:10-20) in order to fight against Satan and his angels, to put to death our sinful dispositions (Rom. 8:13; Col. 3:5). We can win this battle, not by the sword, but by truth, righteousness, the gospel, faith, salvation. Our only offensive weapons are the Word of God and prayer. This may seem a puny arsenal to the rulers of this world, but God tells us that it has more power than any of those rulers. People sometimes say mockingly, “Well, we can always try prayer.” But God’s weapons are more powerful than anything in the mockers’ arsenal. A gun will subdue a man, but only the sword of God’s Word wielded in prayer, will subdue Satan.

John M. Frame, Systematic Theology, 988.