A.T. Robertson Commentary John 3:14

"And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up;" — John 3:14 (ASV)

Moses lifted up the serpent (Μωυσης υψωσεν τον οφιν). Reference to Nu 21:7ff. where Moses set the brazen serpent upon the standard that those who believed might look and live. Jesus draws a vivid parallel between the act of Moses and the Cross on which he himself (the Son of man) "must" (δε, one of the heavenly things) "be lifted up" (υψωθηνα, first aorist passive infinitive of υψοω, a word not used about the brazen serpent). In John υψοω always refers to the Cross (8:28; 12:32,34), though to the Ascension in Acts (Acts 2:33; Acts 5:31). Jesus is complimenting the standing and intelligence of Nicodemus as "the teacher of Israel" by telling him this great truth and fact that lies at the basis of the work of the kingdom of God (the atoning death of Christ on the Cross).