By John Piper
In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; and take the helmet of salvation, and the sword of the Spirit, which is the word of God.(Ephesians 6:16–17)
When I am anxious about getting old, I battle unbelief with the promise, “Even to your old age I am he, and to gray hairs I will carry you. I have made, and I will bear; I will carry and will save” (Isaiah 46:4).
When I am anxious about dying, I battle unbelief with the promise that “none of us lives to himself, and none of us dies to himself. For if we live, we live to the Lord, and if we die, we die to the Lord. So then, whether we live or whether we die, we are the Lord’s. For to this end Christ died and lived again, that he might be Lord both of the dead and of the living” (Romans 14:7–9).
When I am anxious that I may make shipwreck of faith and fall away from God, I battle unbelief with the promises, “He who began a good work in you will bring it to completion at the day of Jesus Christ” (Philippians 1:6); and, “He is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them” (Hebrews 7:25).
Join me in this battle! Let us make war, not with other people, but with our own unbelief. Unbelief in the promises of God is the root of anxiety, which, in turn, is the root of so many other sins. The sword of the Spirit is the word of God, Paul said in Ephesians 6:17. The shield by which we quench Satan’s fiery deceits is faith (verse 16) — faith in that very word of God. So take up the shield in your left hand and the sword in your right hand, and let us fight the good fight of faith.
Take up the Bible, ask the Holy Spirit for help, lay the promises up in your heart, and fight the good fight — to live by faith in future grace.