The Christian soldier experiences salvation in the present. If in the past he was delivered from the penalty of sin, in the present he is being delivered from the power of sin. He needs to be delivered from this power because it is an ally of the devil and will do its utmost to cause the Christian to fall. Therefore the Christian soldier must weaken this indwelling power.
Strong though this power is, it is not stronger than the resources the Christian soldier has at his disposal. Each believer possesses the power of the indwelling Spirit, who, as the apostle John says in 1 John 4:4, is ‘greater than he who is in the world’. The Spirit enables the believer to put to death heart sins and replace them with holy characteristics. This activity of the Spirit in each believer’s life is a constant one, although it is the case that believers can grieve the Spirit by their sins and they will not know his power overcoming such sins until they repent of them. This does not mean that a believer can ever be in a state, in this life, of not having to repent of personal sins. But there is a big difference between a believer fighting against inward sin, such as wrong thoughts, and a believer ignoring them. Repentance for such sins is accompanied by spiritual power to overcome the sins.
When under attack, the Christian soldier should cry to God for divine aid by the Spirit. At the same time he should remind himself of the power of the Spirit, perhaps recalling the way he worked in the lives of biblical characters, even in those, such as David, who were overcome by a sin. Further, he can see the way he is working in the lives of his fellow-soldiers, which can be a useful means of encouragement.
It is crucial for the Christian soldier that this second aspect of salvation be maintained in a lively spiritual manner. Peter shows its importance in 2 Peter 1:1-11 where he urges his readers to continue adding Christian graces to their characters. He stresses that if a Christian fails to do this, he will develop a bad memory and also become short-sighted: ‘For whoever lacks these qualities is so nearsighted that he is blind, having forgotten that he was cleansed from his former sins’ (v. 9). Failure to look up results in inability to look back or to look far ahead.