The most difficult fights are not the wars that ravish the world, but the individual battles for control of our souls. Because of our sinful bent, we don’t even need the Devil and his demons’ additional efforts in causing us to sin. Temptation to sin comes from all places, not to mention our own desires (James 4:1).
The armour to stand strong amidst trial and temptation is given in detail in Ephesians 6, but already in Ephesians 4 the basic training for fighting sin is given. Ephesians 4 contains the textbook lecture needed before entering the armoury in chapter 6.
In three verses the Holy Spirit gives us the three basic rules of sin-fighting
to put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires, and
to be renewed in the spirit of your minds, and
to put on the new self, created after the likeness of God in true righteousness and holiness.
Don’t even think of being victorious over sin in the moment of temptation if you do not hold to these three rules of sin-fighting.
To stay holy and pure in a world of sin, ruled by the power of darkness, and tempted by the desires of your fallen nature is going to require an undying commitment to put off sin as though it were a disgusting shirt, to renew your mind in how you think about the sin and about Christ, and to put on the righteous counterpart of the sin in that moment.
Ephesians 4 is not only a lecture of teaching the basics, but is one of the lectures that makes practical sense, for it offers many examples of what this looks like.
Take for example the sin of lying.
Therefore, having put away falsehood, let each one of you speak the truth with his neighbor, for we are members one of another.
In the moment of being tempted to lie, put off the lying, and put on saying what is true. To make this easier, it helps to renew your mind by thinking that we are all interdependent on each other, so we cannot practise something as divisive as lying when truth will build trust, unity, and openness.
Or how about the sin of stealing?
Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear.
When tempted to blurt out a hurtful, impure, or ill-motived saying, don’t; instead, let only the good sentences come out of your mouth. Limit your saying to that which builds the listener up and is said at the appropriate time. To make this easier, think of words as grace-dispensers; all your words need to be gracified before exiting your mouth.
Take the sin you struggle to fight in the moment of temptation, and identify the put off, put on, and renew your mind rules for that sin, and go, be holy as our Saviour and God is holy.