Isaiah 61:10: "I will greatly rejoice in the LORD; my soul shall exult in my God, for he has clothed me with the garments of salvation; he has covered me with the robe of righteousness, as a bridegroom decks himself like a priest with a beautiful headdress, and as a bride adorns herself with her jewels."
Hebrews 12:24: "and to Jesus, the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel."
1 John 1:7: "But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin."
Revelation 7:9-14: "9 After this I looked, and behold, a great multitude that no one could number, from every nation, from all tribes and peoples and languages, standing before the throne and before the Lamb, clothed in white robes, with palm branches in their hands, 10 and crying out with a loud voice, 'Salvation belongs to our God who sits on the throne, and to the Lamb!' 11 And all the angels were standing around the throne and around the elders and the four living creatures, and they fell on their faces before the throne and worshiped God, 12 saying, 'Amen! Blessing and glory and wisdom and thanksgiving and honor and power and might be to our God forever and ever! Amen.'
"13 Then one of the elders addressed me, saying, 'Who are these, clothed in white robes, and from where have they come?' 14 I said to him, 'Sir, you know.' And he said to me, 'These are the ones coming out of the great tribulation. They have washed their robes and made them white in the blood of the Lamb."
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The text is public domain:
Jesus, Thy blood and righteousnessMy beauty are, my glorious dress;Midst flaming worlds, in these arrayed,With joy shall I lift up my head.
Bold shall I stand in that great day,Cleansed and redeemed, no debt to pay;Fully absolved through these I amFrom sin and fear, from guilt and shame.
Lord, I believe Thy precious blood,Which at the mercy seat of GodPleads for the captives' liberty,Was also shed in love for me.
Lord, I believe, were sinners moreThan sands upon the ocean shore,Thou hast for all a ransom paid,For all a full atonement made.
When from the dust of death I riseTo claim my mansion in the skies,Then then shall be my only plea:Jesus hath lived and died for me.
Jesus, be endless praise to Thee,Whose boundless mercy hath for me,For me, and all Thy hands have made,An everlasting ransom paid.
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The Biblical sources for this hymn appear mostly in the first half. The first two verses use the images from Isaiah 61:10 and the white robes from the passage from Revelation 7. The hymn's third verse seems to combine the verses from Hebrews 12:24 and 1 John 1:7. Part of Revelation 7 could also be cited for "Jesus, be endless praise to Thee" in the last verse.
The phrase "the captives' liberty" in the third verse bears some resemblance to part of Isaiah 61:1: "The Spirit of the Lord GOD is upon me, because the LORD has anointed me to bring good news to the poor; he has sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to those who are bound," which Jesus quotes in Luke 4:18.
The lines "When from the dust of death I rise / To claim my mansion in the skies" in the fifth verse seem to refer to John 14:2: "'In my Father's house are many rooms. If it were not so, would I have told you that I go to prepare a place for you?'"