2 King 2:1-15: "1 Now when the LORD was about to take Elijah up to heaven by a whirlwind, Elijah and Elisha were on their way from Gilgal. 2 And Elijah said to Elisha, 'Please stay here, for the LORD has sent me as far as Bethel.' But Elisha said, 'As the LORD lives, and as you yourself life, I will not leave you.' So they went down to Bethel. 3 And the sons of the prophets who were in Bethel came out to Elisha and said to him, 'Do you know that today the LORD will take away your master from over you?' And he said, 'Yes, I know it; keep quiet.'
"4 Elijah said to him, 'Elisha, please stay here, for the LORD has sent me to Jericho.' But he said, 'As the LORD lives, and as you yourself live, I will not leave you.' So they came to Jericho. 5 The sons of the prophets who were at Jericho drew near to Elisha and said to him, 'Do you know that today the LORD will take away your master from over you?' And he answered, 'Yes, I know it; keep quiet.'
"6 Then Elijah said to him, 'Please stay here, for the LORD has sent me to the Jordan.' But he said, 'As the LORD lives, and as you yourself live, I will not leave you.' So the two of them went on. 7 Fifty men of the sons of the prophets also went and stood at some distance from them, as they both were standing by the Jordan. 8 Then Elijah took his cloak and rolled it up and struck the water, and they water was parted to the one side and to the other, till the two of them could go over on dry ground.
"9 When they had crossed, Elijah said to Elisha, 'Ask what I shall do for you, before I am taken from you.' And Elisha said, 'Please let there be a double portion of your spirit on me.' 10 And he said, 'You have asked a hard thing; yet, if you see me as I am being taken from you, it shall be so for you, but if you do not see me, it shall not be so.' 11 And as they still went on and talked, behold, chariots of fire and horses of fire separated the two of them. And Elijah went up by a whirlwind into heaven. 12 And Elisha saw it and he cried, 'My father, my father! The chariots of Israel and its horsemen!' And he saw him no more.
"Then he took hold of his own clothes and tore them in two pieces. 13 And he took up the cloak of Elijah that had fallen from him and went back and stood on the bank of the Jordan. 14 Then he took the cloak of Elijah that had fallen from him and struck the water, saying, 'Where is the LORD, the God of Elijah?' And when he had struck the water, the water was parted to the one side and to the other, and Elisha went over.
"15 Now when the sons of the prophets who were at Jericho saw him opposite them, they said, 'The spirit of Elijah rests on Elisha.' And they came to meet him and bowed to the ground before him."
John 20:21-23: "21 Jesus said to them again, 'Peace be with you. As the Father has sent me, even so I am sending you.' 22 And when he had said this, he breathed on them and said to them, 'Receive the Holy Spirit. 23 If you forgive the sins of any, they are forgiven them; if you withhold forgiveness from any, it is withheld.'"
John 17:18: "'As you sent me into the world, so I have sent them into the world.'"
1 Timothy 4:13-16: "13 Until I come, devote yourself to the public reading of Scripture, to exhortation, to teaching. 14 Do not neglect the gift you have, which was given you by prophecy when the council of elders laid their hands on you. 15 Practice these things, immerse yourself in them, so that all may see your progress. 16 Keep a close watch on yourself and on the teaching. Persist in this, for by so doing you will save both yourself and your hearers."
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The text is public domain:
God of the prophets, bless the prophets' sons;Elijah's mantle o'er Elisha cast.Each age its solemn task may claim but once;Make each one nobler, stronger than the last.Anoint them prophets, men who are intentTo be Your witnesses in word and deed,Their hearts aflame, their lips made eloquent,Their eyes awake to ev'ry human need.Anoint them priests, strong intercessors they,For pardon and for love and hope and peace,That, through their pleading, guilty sinners mayFind Jesus' mercy and from sin release.Anoint them kings, yes, kingly kings, O Lord.Anoint them with the Spirit of Your Son.Theirs not a jeweled crown, a blood-stained sword;Theirs, by sweet love, for Christ a kingdom won.Make them apostles, heralds of Your cross;Forth let them go to tell the world of grace.Inspired by You, may they count all but lossAnd stand at last with joy before Your face.
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The long passage from 2 Kings 2 is cited apparently just to give context for the line "Elijah's mantle o'er Elisha cast" in the first verse. The two passages from John (chapters 17 and 20) both appear in the line "Forth let them go to tell the world of grace" in the last verse. The passage from John 20 also seems to be referred to in the third verse, which is about forgiveness.
The passage from 1 Timothy 4 seems to be the basis for the hymn text, although no specific words or phrases from it appear in the hymn text.
The line "Inspired by You, may they count all but loss" in the last verse comes from Philippians 3:8: "Indeed, I count everything as loss because of the surpassing worth of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things and count them as rubbish, in order that I may gain Christ."