Romans 5:9-10: "9 Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God. 10 For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life."
1 Corinthians 11:23-29: "23 For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when he was betrayed took bread, 24 and when he had given thanks, he broke it, and said, 'This is my body which is for you. Do this in remembrance of me.' 25 In the same way also he took the cup, after supper, saying, 'This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.' 26 For as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes.
"27 Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty concerning the body and blood of the Lord. 28 Let a person examine himself, then, and so eat of the bread and drink of the cup. 29 For anyone who eats and drinks without discerning the body eats and drinks judgement on himself."
John 6:50-57: "50 'This is the bread that comes down from heaven, so that one may eat of it and not die. 51 I am the living bread that came down from heaven. If anyone eats of this bread, he will live forever. And the bread that I will give for the life of the world is my flesh.'
"52 The Jews then disputed among themselves, saying, 'How can this man give us his flesh to eat?' 53 So Jesus said to them, 'Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. 54 Whoever feeds on my flesh and drinks my blood has eternal life, and I will raise him up on the last day. 55 For my flesh is true food, and my blood is true drink. 56 Whoever feeds on my flesh and drinks my blood abides in me, and I in him. 57 As the living Father sent me, and I live because of the Father, so whoever feeds on me, he also will live because of me.'"
1 John 1:9: "If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness."
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Only some of the verses are public domain:
1 Jesus Christ, our blessed Savior,Turned away God's wrath forever;By His bitter grief and woeHe saved us from the evil foe.
2 As His pledge of love undying,He, this precious food supplying,Gives His body with the bread,And with the wine the blood He shed.
4 Praise the Father, who from heavenTo His own this food has given,Who, to mend what we have done,Gave into death His only Son.
5 Firmly hold with faith unshakenThat this food is to be takenBy the sick who are distressed,By hearts that long for peace and rest.
7 Christ says: "Come, all you that labor,And receive My grace and favor:Those who feel no pain or illNeed no physician's help or skill."
9 If your heart this truth professesAnd your mouth your sin confesses,You will be your Savior's guest,Be at His banquet truly blest.
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Romans 5:9-10 appears in the first verse and the second half of the fourth verse.
The passages from 1 Corinthians 11:23-29 and John 6:50-57 are the primary sources for the hymn. They appear in most of the verses and especially in the second and third. The third and sixth verses are drawn specifically from 1 Corinthians 11:27-29.
1 John 1:9 is in the ninth verse, although the hymn seems also to incorporate Romans 10:10: "For with the heart one believes and is justified, and with the mouth one confesses and is saved."
The beginning of the seventh verse ("Christ says: 'Come, all you that labor, / And receive My grace and favor'") seems to be patterned on Matthew 11:28: "'Come to me, all who labor and are heavy laden, and I will give you rest.'"