Isaiah 59:17
14 Justice is driven back; godliness stands far off. Indeed, honesty stumbles in the city square and morality is not even able to enter. 15 Honesty has disappeared; the one who tries to avoid evil is robbed. The Lord watches and is displeased, for there is no justice. 16 He sees there is no advocate; he is shocked that no one intervenes. So he takes matters into his own hands; his desire for justice drives him on. 17 He wears his desire for justice like body armor, and his desire to deliver is like a helmet on his head. He puts on the garments of vengeance and wears zeal like a robe. 18 He repays them for what they have done, dispensing angry judgment to his adversaries and punishing his enemies. He repays the coastlands.
Ephesians 6:13
10 Finally, be strengthened in the Lord and in the strength of his power. 11 Clothe yourselves with the full armor of God, so that you will be able to stand against the schemes of the devil. 12 For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world rulers of this darkness, against the spiritual forces of evil in the heavens. 13 For this reason, take up the full armor of God so that you may be able to stand your ground on the evil day, and having done everything, to stand. 14 Stand firm therefore, by fastening the belt of truth around your waist, by putting on the breastplate of righteousness, 15 by fitting your feet with the preparation that comes from the good news of peace, 16 and in all of this, by taking up the shield of faith with which you can extinguish all the flaming arrows of the evil one. 17 And take the helmet of salvation and the sword of the Spirit (which is the word of God).
Notes and References
"... It is interesting that we find the use of a bit of this imagery applied to ordinary Christian believers in Ephesians 6:13–17 where it is called the armor of God. Much more needs to be said however because in fact there is an abundant use of Isaiah in Ephesians, including in this passage (compare Isaiah 59:17; 52:7), and furthermore, as Frank Thielman says, it would appear that Paul is not drawing directly on Isaiah here, but rather Isaiah as filtered through and used in later Jewish literature. For example, the author of Wisdom of Solomon speaks of the Lord fighting his enemies by taking zeal as his whole armor and putting on righteousness as a breastplate, impartial justice as a helmet, holiness as an invincible shield, and wrath for a sword (Wisdom of Solomon 5:18–20). On one point Paul is closer to Isaiah than to Wisdom of Solomon, namely connecting salvation with the helmet (Isaiah 59:17; Eph 6:17) but mostly he is closer to Wisdom of Solomon in his use of these images ..."
Witherington, Ben Isaiah Old and New: Exegesis, Intertextuality, and Hermeneutics (p. 111) Fortress Press, 2017