10 Finally, be strong in the Lord and in the strength of his might. 11 Put on the whole armour of God, that you may be able to stand against the schemes of the devil.12 For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. 13 Therefore take up the whole armour of God, that you may be able to withstand in the evil day, and having done all, to stand firm. 14 Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, 15 and, as shoes for your feet, having put on the readiness given by the gospel of peace. 16 In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one;17 and take the helmet of salvation, and the sword of the Spirit, which is the word of God, 18 praying at all times in the Spirit, with all prayer and supplication. To that end, keep alert with all perseverance, making supplication for all the saints."
Ephesians 6:10-18
The great, inescapable question, the ultimate question for every man is: 'How do I stand before God?' This is Paul's theme in the Epistle to the Romans, and he answers that question in the proclamation of the good news of the gospel, that God accepts the sinner as righteous, for Christ's sake. Man the sinner is guilty in the sight of God, and stands condemned at the bar of divine justice (the picture Paul uses is from the law courts and his language is couched in legal, 'forensic' terms). The incomparable message of the gospel is that the guilty sinner is acquitted by God and accepted as righteous in His sight because of what Christ has done in His death and resurrection. The question inevitably arises, 'How can a holy God justify and acquit the guilty and still remain just without mocking the inviolable laws of the universe?' The answer Paul gives to this in Romans 3 is through Jesus Christ, 'Whom God has set forth as a propitiation through faith in His blood ... to declare His righteousness: that He might be just, and the justifier of him which believeth in Jesus'. God, as Creator and Law-giver has a right to expect from man obedience to His laws and loyalty and devotion to His Person. But man through sin has deprived God of both these things, so that over against man there stands both a broken law and a broken relationship. Man therefore has a twofold need if he is to be put right with God: something to deal with his guilt and something to enable him to fulfil his obligation to God in terms of righteousness and devotion to Him. It is this twofold task that Christ took upon Himself for our sakes. On the one hand He bore our condemnation, standing in for us and sealing our pardon with His blood; on the other hand He offered Himself without spot to God for us, offering His perfect righteousness in place of our sin. As Paul puts it in 2 Corinthians 5:21, 'God hath made Him to be sin for us, who knew no sin; that we might be made the righteousness of God in Him'. A great, divine exchange took place, in which 'the Lord laid on Him the iniquity of us all', and His righteousness was laid upon ('imputed to') us. This is the glory, the wonder, and the marvel of the gospel of redeeming grace!