Biblical citations in the hymnal:
Psalm 46:1, 7, 11;
Revelation 19:11-16;
Romans 8:31-39;
Ephesians 6:10-17
Psalm 46:1: "God is our refuge and strength, a very present help in trouble."
Psalm 46:7: "The LORD of hosts is with us; the God of Jacob is our fortress."
Psalm 46:11: "The LORD of hosts is with us; the God of Jacob is our fortress."
Revelation 19:11-16: "11 Then I saw heaven opened, and behold, a white horse! The one sitting on it is called Faithful and True, and in righteousness he judges and makes war. 12 His eyes are like a flame of fire, and on his head are many diadems, and he has a name written that no one knows but himself. 13 He is clothed in a robe dipped in blood, and the name by which he is called is The Word of God. 14 And the armies of heaven, arrayed in fine linen, white and pure, were following him on white horses. 15 From his mouth comes a sharp sword with which to strike down the nations, and he will rule them with a rod of iron. He will tread the winepress of the fury of the wrath of God the Almighty. 16 On his robe and on his thigh he has a name written, King of kings and Lord of lords."
Romans 8:31-39: "31 What then shall we say to these things? If God is for us, who can be against us? 32 He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things? 33 Who shall bring any charge against God's elect? It is God who justifies. 34 Who is to condemn? Christ Jesus is the one who died - more than that, who was raised - who is at the right hand of God, who indeed is interceding for us. 35 Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or danger, or sword? 36 As it is written, 'For your sake we are being killed all the day long; we are regarded as sheep to be slaughtered.' 37 No, in all these things we are more than conquerors through him who loved us. 38 For I am sure that neither death nor life, nor angels nor rulers, nor things present nor things to come, nor powers, 39 nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord."
Ephesians 6:10-17: "10 Finally, be strong in the Lord and in the strength of his might. 11 Put on the whole armor 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 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"
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The hymn appears in different translations as LSB #656 and #657. Only the text of #656 is public domain, however:
A mighty fortress is our God,
A trusty shield and weapon;
He helps us free from ev'ry need
That hath us now o'ertaken.
The old evil foe
Now means deadly woe;
Deep guile and great might
Are his dread arms in fight;
On earth is not his equal.
With might of ours can naught be done,
Soon were our loss effected;
But for us fights the valiant One,
Whom God Himself elected.
Ask ye, Who is this?
Jesus Christ it is,
Of Sabaoth Lord,
And there's none other God;
He holds the field forever.
Though devils all the world should fill,
All eager to devour us,
We tremble not, we fear no ill;
They shall not overpow'r us.
This world's prince may still
Scowl fierce as he will, He can harm us none.
He's judged; the deed is done;
One little word can fell him.
The Word they still shall let remain
Nor any thanks have for it;
He's by our side upon the plain
With His good gifts and Spirit.
And take they our life,
Goods, fame, child, and wife,
Though these all be gone,
Our vict'ry has been won;
The Kingdom ours remaineth.
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The verses from Psalm 46 appear in the first line: "A mighty fortress is our God."
The text from Revelation 19 appears in the second verse: "But for us fights the valiant One... Jesus Christ it is, / Of Sabaoth Lord." The text from Romans 8, particularly the first few verses ("God is for us"), figures into this a bit too, and the second half (roughly verses 35 to 39) seems to appear in the third verse: "We tremble not, we fear no ill; / They shall not overpowe'r us... He can harm us none."
The armor of God from Ephesians 6 is referred to in the line "A trusty shield and weapon" in the first verse and perhaps also "He can harm us none" in the third verse.
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The lines "Ask ye, Who is this? / Jesus Christ it is, / Of Sabaoth Lord" in the second verse bear some resemblance to Psalm 24:8, 10: "8 Who is the King of glory? The LORD, strong and mighty, the LORD, mighty in battle! 10 Who is this King of glory? The LORD of hosts, he is the King of glory!"
The description of "devils... eager to devour us" at the beginning of the third verse is drawn from 1 Peter 5:8: "Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour."