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
But we can go further than what was said at the end of the previous Note. Hearts and lives gripped and mastered in this way by the truth of the gospel are hearts and lives that are invincible, and impregnable by the attacks of the enemy. Indeed, it is possible, to be more specific still, there is what we could call 'battle-truth', there is that body of truth that is so essential for mature Christian experience, given by Paul, for example, in the Epistle to the Romans. It is hardly possible to be a good soldier of Jesus Christ without having made it one's business to grasp the teaching of this mighty epistle and be mastered by it. To live much in the atmosphere of this apostolic teaching will mean to be girt about with truth in such a way as to be able to resist all the enemy's attacks.
It is at this point that we see the necessary link between truth of doctrine and truth of heart. For it is simply not possible to allow ourselves to be gripped and mastered by the truth of God without thereby being made true men and women whose lives are marked by probity and integrity. We sometimes sing the words,
But who can fight for truth and God
Enthralled by lies and sin?
He who would wage such war on earth
Must first be true within.
The Psalmist says, 'Behold, Thou desirest truth in the inward parts, and in the hidden parts Thou shalt make me to know wisdom" (Psalm 51:6). David is brokenly confessing his sins in these words, recognising that his real problem lay in the lie that was hidden in his heart, which finally erupted into the action that destroyed his testimony. He was not true within, for deep down there were polluted things that held empire over his soul, and finally brought him crashing down.
Much more could, of course, be said on this subject (and has been said in the book The Christian Warfare and Armour), but these Readings have sufficiently indicated the meaning of the phrase 'loins girt about with truth' to enable us to turn to the next part of the armour in the next Note.