20 And there were certain Greeks among them that came up to worship at the feast:

[Certain Greeks] Three likely possibilities; 1. Proselytes, gentiles who had converted to the Jewish religion, who came to worship the true God at the feast; 2. Jews who lived in the Grecian provinces and spoke the Greek language, or 3. Gentiles, who never knew the true God, and, hearing of the temple and the miracles of our Lord, came to investigate and to offer sacrifices and worship according to the manner of the people of the land.

21 The same came therefore to Philip, which was of Bethsaida of Galilee, and desired him, saying, Sir, we would see Jesus.

[Sir, we would see Jesus] We have heard much concerning him and wish to meet the person of whom we have heard these strange things. The salvation of the soul often originates, under God, as a matter of curiosity. Many have only wished to see one who speaks much of Jesus, his miracles and mercies; and in hearing have felt the powers of the world to come and have become genuine converts to the truth of the Gospel.

22 Philip cometh and telleth Andrew: and again Andrew and Philip tell Jesus.

[Andrew and Philip tell Jesus] How pleasing to God is this union, when the ministers of his Gospel agree to unite together to bring souls to Christ

23 And Jesus answered them, saying, The hour is come, that the Son of man should be glorified.

[The hour is come] In response to this inquiry Jesus answered with the announcement that, "The hour is come, that the Son of man should be glorified." A momentous time in history is about to begin. The Gospel shall be preached to all the nations, the division between Jews and Gentiles shall be removed and all who believe shall be gathered into one fold. See Galatians 3:28 and Ephesians 2:11-18.

24 Verily, verily, I say unto you, Except a corn of wheat fall into the ground and die, it abideth alone: but if it die, it bringeth forth much fruit.

Our lord compares himself to a grain of wheat; his death, to a grain sown and decomposed in the gound; his resurrection to the blade which springs up from the dead grain; which grain, thus dying, brings forth an abundance of fruit.
In comparing himself to that grain of wheat our Lord shows us: 1. The cause of his death - the will of God who set that price for the redemption of the world. 2. The result of his death - the redemption of a lost world; the justification, sanctification and glorification of all individuals who believe. See John 3:16.

25 He that loveth his life shall lose it; and he that hateth his life in this world shall keep it unto life eternal.

Temporal vs eternal values. Many, who love this world and their lives in it, miss eternal life because their attention is riveted upon the present. They have no time for God and the study of his Word, and do not wish to be constricted by Holy living. Others, who have the good fortune of knowing and believing in Christ realize that this current life is only temporary, and is not to be compared with what awaits us in the future.

26 If any man serve me, let him follow me; and where I am, there shall also my servant be: if any man serve me, him will my Father honour.

Christ is a master in a two fold sense: 1. To instruct men, and 2. to employ and appoint them their work.
He who wishes to serve Christ must become: 1. His disciple or scholar, that he may be taught; 2. His servant, that he may be employed and obey his master.
To such a person a twofold promise is given: 1. He shall be with Christ, in eternal fellowship with him; and 2. He shall be honored by God. He shall have an abundant reward in glory. How great? "Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him." 1 Corinthians 2:9. Compare with Isaiah 64:4.

27 Now is my soul troubled; and what shall I say? Father, save me from this hour: but for this cause came I unto this hour.

Our blessed Lord took upon himself our weaknesses. As a man he was troubled at the prospect of a violent death. Yet he pointed out that it would not be appropriate for him to change his mind and pray for release from his task.

28 Father, glorify thy name. Then came there a voice from heaven, saying, I have both glorified it, and will glorify it again.

Christ here teaches a lesson in submission to the Divine will. Do with me what you will that your name might be glorified. Then came a voice from heaven affirming Jesus commitment and the Father's agreement.

29 The people therefore, that stood by, and heard it, said that it thundered: others said, An angel spake to him.
30 Jesus answered and said, This voice came not because of me, but for your sakes.

One more miracle to attest to the observers that Jesus was in truth the Son of God and in compliance with his Father's plan.