We see in Jn 9:4-5 (NIV) Jesus giving a prelude to the healing of a man born blind:
As long as it is day, we must do the works of him who sent me. Night is coming, when no one can work. While I am in the world, I am the light of the world.”.
My question is : Why did Jesus say that he is the light of the world while he is in it ? What happens after his ascension ?
Christ, while living on earth, was reminding Israel of part of God's plan at that moment. Specifically, Christ was/is the only path to God. Christ was teaching Israel how to present the gospel of God's coming kingdom to the world. He would save "His people" from their sins against God, and through hearing this good news of Christ (the Light) Israel would bring the world to God.
Matthew 1:21-23
21 And she shall bring forth a son, and thou shalt call his name Jesus: for he shall save his people from their sins.
22 Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying,
23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
God's secret ("the gift" to the world and still hidden at that moment) was that the entire world would be forgiven of their sins through Christ and His blood at His death on the cross, and without first having to go through Israel to receive the now purchased gift of forgiveness.
Romans 16:25-27
25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,
26 But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:
27 To God only wise, be glory through Jesus Christ for ever. Amen.
1 Corinthians 2:7-8
7 But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:
8 Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory.
Christ, ascended in heaven (opposite to "the world while He was in it"), appointed Paul as His messenger to reveal God's once hidden, "but now made manifest", "secret" and thus, "fulfill the word of God" (Col 1:25). This is the gospel of God's grace that Paul implores Christians to now teach; Christ crucified for our sins, rather than God's "coming kingdom" message to Israel and "Emmanuel" (God with us).
God's beacon of Light now emits from Christ on the cross, where God forgave the sins of the world through Christ's shed blood. It was the purchase of the gift that is received by having this faith alone in Him alone.
Romans 3:25
Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
The grammatical construction here is problematic, for the plain sense of the text implies that there will be a time (after Jesus no longer remains in the world) that he will no longer be a light to it. Commentators use various interpretive methods to explain this:
It refers to the healing miracle he was about to perform, of giving sight to the blind, which he would no longer perform after his death. Once Jesus ascended, he would no longer perform these kinds of miracles.
It refers to his role of bring spiritual light to the world. His life on earth could not last forever. Thus, in John's gospel, he concludes his life on earth with the words "it is finished." His example, however, continues to inspire believers.
Some specific examples:
Expositor's: 'The “when” seems to be used to suggest a time when He should not be in the world: “when I am in the world, I am the Light of the World,” as He immediately illustrated by the cure of the blind man.'
Jamieson-Fausset-Brown: "Not if He would cease, after that, to be so; but that He must make full proof of His fidelity while His earthly career lasted by displaying His glory."
Meyer: "He was soon to depart from the world, and... the present mode and action of the [light], which were bound up with His corporeal earthly career, must come to an end. Then Christ would work through the Paraclete and through the vehicles of the Paraclete, as the Light of the world.
Conclusion: Some commentators understand this verse to refer to the immediate context of healing the blind man. Such miracles would cease once Jesus was no longer "in the world." Others understand it to refer to his role of bringing spiritual light to the world, which was demonstrated by his earthly life but continues to this day. I see no reason which these approaches should be understood as mutually exclusive.
Yes, the verse in question states that while Jesus was still on Earth he said he is the light of the world. But to understand why he could say that, the significance and depth of meaning, we have to look elsewhere in John's gospel, for the verse in question does not tell us why. John's readership already knew the prelude to the arrival of Christ into our world, with regard to light. John first speaks of him as the Word who made everything that was made, adding:
"In him was life; and the life was the light of men, and the light in the darkness did shine, and the darkness did not perceive it." John 1:4 Y.L.T.
The Word incarnated with the miraculous conception in the virgin Mary's womb, being the man-child born to Mary, Jesus. John the Baptist came to testify to him, "the true Light, which doth enlighten every man, coming to the world" (John 1:9 Y.L.T.) The Baptist stressed that he came to testify to that true Light (which was not himself).
With that in mind, the true Light, who had come into the world, was indeed the light of this sin-darkened world. But darkness does not comprehend that spiritual Light.
It was still 'day' (spiritually speaking) for as long as Jesus was in the world, but after his death, resurrection and ascension, he was no longer walking on this Earth. However, those who believed in his name, receiving him in faith, had that light of life given to them. The light of the gospel began to shine through their witness, exposing the darkness of sin, as 2 Corinthians 4:4 states. They no longer walked in the vanity of minds darkened because of the blindness of their heart (Ephesians 4:18). As Paul explained,
"For ye were once darkness, and now light in the Lord; as children of light walk ye." Ephesians 5:8 Y.L.T.
In another letter, he said they were to be blameless and harmless, children of God, even though living in a sin-darkened world, shining like stars in the world, holding forth the word of life. (Philippians 2:15-16)
That answers the other question as to what happened regarding this spiritual light, after Christ's ascension.
John 9:5 contains a verb subtlety that is difficult to convey into English. The Greek is:
Ὅταν ἐν τῷ κόσμῳ ὦ, φῶς εἰμι τοῦ κόσμου.
There are two forms of the verb "I am" here; one subjunctive active, and the other aorist active. Here is my attempt at conveying the meaning:
While I can be in the world, I am the light of the world.
Jesus appears to be alluding to two things:
There appears to be a reference to His earlier statement that:
Therefore Jesus spoke to them again, saying, "I am the light of the world. The one following Me shall not walk in the darkness, but will have the light of life."
That is, Jesus is the source of spiritual light; but the only ones who "see" that light are those who elect to accept and follow Jesus.
Thus, Jesus' time as the light of the world was limited to His physical presence while on earth. However, following His resurrection and return to heaven, the Advocate, the Spirit of Truth, the Holy Spirit, would replace Jesus as the teacher of people about Jesus the source of spiritual truth.
The reason for this is not hard to find. Note the important statement that Jesus made to the disciples following His resurrection and appearance to them in Luke 24:39 -
See my hands and my feet, that it is I myself. Touch me, and see. For a spirit does not have flesh and bones as you see that I have.”
That is, Jesus, when speaking to people was limited to His physical presence because of His "flesh and bone". By contrast, the Holy Spirit could be omnipresent and teach all who are willing.
