Ephesians 6:13–18 (ESV)
13 Therefore take up the whole armor 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
 
Paul has established the reason why we must put on the whole armor of God. We must be ready to stand against the devil when the evil day comes.  The evil day probably refers to any time when the enemy comes against us like a flood. Satanic opposition seems to occur in waves, advancing and receding. Even after our Lord’s temptation in the wilderness, the devil left Him only for a season (Luke 4:13).
 
Before we examine the armor in detail, It is important to notice when we are to put on the armor. 
Notice the phrases,  “having fastened on the belt of truth,” “having put on the breastplate of righteousness,” “having put on the readiness,” “in all circumstances.”
 
These phrases imply we are dressed and ready before the attack comes. The implication is that we must not wait until the day of evil comes upon us to put our fighting equipment on, but we are to wear it at all times so that we are already prepared for those evil moments.
 
So, what is the significance of each part of the armor? Let’s examine.
 
It may appear that there are six weapons of war, but as we shall see, there are actually seven. For though Paul does not use a weapon metaphor, surely prayer is the seventh and overarching weapon.
 
Paul begins in a logical order and links the first three together and, in the same way, links the next three together.
 
1.  “having fastened on the belt of truth”
The first piece of armor mentioned is the belt of truth. The scabbard of the sword and his breastplate were attached to the soldier’s belt. This gave him freedom of movement. Others may guess and grope; the Christian moves freely and quickly because he knows the truth. 
 
Certainly, we must be faithful in holding the truth of God’s word, but it is also necessary for the truth to hold us. We must apply it to our daily lives. As we test everything by the truth, we find strength and protection in the combat.
 
If we do not know the truth about our situations, we cannot assess how to respond. If we do not live the truth, we nullify our fellowship with the Lord and are therefore unable to see clearly how to fight our battles.
 
Jesus said, “If you abide in my word, you are truly my disciples, and you will know the truth, and the truth will set you free.” (John 8:31–32). There is no greater freedom than what Jesus gives.  He has set us free from the power of sin and He has set us free from the penalty of sin and death.  We are free to become all He has made us to be and free to do all that He has called us to do. And all of this is connected to living in tune with Jesus who is “the Way, the Truth and the Life (John 14:6).”
 
Is there any wonder why Paul placed truth first, since all the other armor is dependent upon this?