It is obvious from the context of verses 14 and 15 that the meaning of Jesus’ being “lifted up” is the image of him being crucified and “lifted up” on the cross. It may be, however, that it involves more than this. In order to fulfill the Atonement and “draw all men” unto him, it was requisite that he be “lifted up” as a light to the world—that his example and teachings might draw men to him, and he be lifted up into heaven as a glorified God who has fulfilled the commandment given him of the Father.
Each of these images—his perfect example, his death on the cross, and his glorified ascension into heaven—helps us to see how his being lifted up brings us to him and lifts us up, not only to eternal life in the world to come but to a more abundant file in this moral sphere (see John 10:10).