‘And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up that whoever believes in him may have eternal life.'
The fourth mystery is the greatest of all. That this Son of Man must be lifted up on show, as a means of salvation. ‘As Moses lifted up the serpent in the wilderness (Numbers 21:9) so must the Son of Man be lifted up, that whoever believes in Him may have eternal life'. In the wilderness the bronze serpent was lifted up at a time when the people were being punished by a plague of snakes because of their unbelief, and when they looked to it they were healed. Thus too the Son of Man must be ‘lifted up' and looked to for salvation.
At this stage ‘lifted up' would not be fully understood, but later we learn fully what it means. He will be lifted up on the cross to die (John 8:28; John 12:32-33), and men must look to Him as the crucified Saviour. This is Heaven's greatest mystery, that through His sacrifice of Himself life will come to all who believe in Him, and look to Him for salvation.
So the Son of Man, who is a citizen of heaven, has come down from heaven (v13) so that He might be “lifted up”, in order that those who believe in him might have ‘eternal life', the life of the age to come, the life of the Spirit.
The word ‘eternal' (literally “of the ages”) focused in Jewish thinking more on the future ‘coming age' than on the Greek conception of eternity, although that coming age was of course seen as being everlasting, and that age would be supremely the age of the Spirit. But the idea behind the ‘life of the age to come' was mainly of the quality of that life.
The Pharisees also had hopes of eternal life, but they hoped to achieve it by obedience to the covenant revealed in their punctilious observance of the Law, and especially of their own interpretations of it. But as the Bible makes clear that way could only lead to hopelessness, for the more they strove the more they failed. In the end the Law they loved so much could only condemn them. So Jesus now tells Nicodemus that what he is hopelessly striving for can be his as a gift if only he responds fully to Him.
We notice here how well this teaching agrees with the other Gospels. There too Jesus speaks of Himself as the Son of Man, stresses that He must suffer, and that finally he will receive His glory and come in that glory from Heaven to judge the world (e.g. Mark 8:31; Mark 14:62; Matthew 25:31). John adds the idea of His position as Judge in John 5:27.