Numbers 21:8
5 And the people spoke against God and against Moses, “Why have you brought us up from Egypt to die in the wilderness, for there is no bread or water, and we detest this worthless food.” 6 So the Lord sent venomous snakes among the people, and they bit the people; many people of Israel died. 7 Then the people came to Moses and said, “We have sinned, for we have spoken against the Lord and against you. Pray to the Lord that he would take away the snakes from us.” So Moses prayed for the people. 8 The Lord said to Moses, “Make a poisonous snake and set it on a pole. When anyone who is bitten looks at it, he will live.” 9 So Moses made a bronze snake and put it on a pole, so that if a snake had bitten someone, when he looked at the bronze snake he lived. 10 The Israelites traveled on and camped in Oboth.
John 3:14
10 Jesus answered, “Are you the teacher of Israel and yet you don’t understand these things? 11 I tell you the solemn truth, we speak about what we know and testify about what we have seen, but you people do not accept our testimony. 12 If I have told you people about earthly things and you don’t believe, how will you believe if I tell you about heavenly things? 13 No one has ascended into heaven except the one who descended from heaven—the Son of Man. 14 Just as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, 15 so that everyone who believes in him may have eternal life.” 16 For this is the way God loved the world: He gave his one and only Son, so that everyone who believes in him will not perish but have eternal life.
Notes and References
"... in addition to the smaller number of quotations, there is also a surprisingly low number of obvious verbal allusions to Israel’s Scripture in John’s Gospel. Or, to put the point more precisely, John’s manner of alluding does not depend upon the citation of chains of words and phrases; instead it relies upon evoking images and figures from Israel’s Scripture. For example, when he writes, “And just as Moses lifted up the serpent in the wilderness, so it is necessary for the Son of Man to be lifted up” (John 3:14), John is clearly alluding to the episode narrated in Numbers 21:8-9, but the only explicit verbal links between the two passages are the name “Moses” and the word “serpent” (ὄφιν). His intertextual sensibility is more visual than auditory ..."
Hays, Richard B. Echoes of Scripture in the Gospels (p. 337) Baylor University Press, 2017