The Cure of a Sick Man at the Pool at Bethzatha
 After this there was a feast of the Jews, and Jesus went up to Jerusalem.  Now there is in Jerusalem by the Sheep Gate a pool, in Hebrew called Bethzatha, which has five porticoes.  In these lay a multitude of invalid, blind, lame, paralyzed.  One man was there, who had been ill for thirty-eight years.  When Jesus saw him and knew that he had been lying there for a long time, He said to him, "Do you want to be healed?"  The sick man answered Him, "Sir, I have no man to put me into the pool when the water is troubled, and while I am going another steps down before me."  Jesus said to him, "Rise, take up your pallet, and walk."  And at once the man was healed, and he took up his pallet and walked.
Now that day was the Sabbath.  So the Jews said to the man who was cured, "It is the Sabbath, it is not lawful for you to carry your pallet."  But he answered them, "The man who healed me said to me, `Take up your pallet, and walk.'"  They asked him, "Who is the man who said to you, `Take up your pallet, and walk'?"  Now the man who had been healed did not know who it was, for Jesus had withdrawn, as there was a crowd in the place.  Afterward, Jesus found him in the temple, and said to him, "See, you are well! Sin no more, that nothing worse befall you."  The man went away and told the Jews that it was Jesus who had healed him.  And this was why the Jews persecuted Jesus, because He did this on the Sabbath.
1. We cannot be certain what festival this was; it probably refers to the Passover, known the world over at the time as the national festival of the Jewish people. But it could refer to another festival, Pentecost, perhaps.
2. This pool was also called the "Probatic" pool because it was located on the outskirts of Jerusalem, beside the Probatic Gate or Sheep Gate (cf. Nehemiah 3:1-32; 12:39) through which came the livestock which was going to be sacrificed in the temple. Around the end of the nineteenth century the remains of a pool were discovered: excavated out of rock, it was rectangular in shape and was surrounded by four galleries or porches, with a fifth porch dividing the pool into two.
3-4. The Fathers teach that this pool is a symbol of Christian Baptism; but that whereas the pool of Bethzatha cured physical ailments, Baptism cures those of the soul; in Bethzatha's case only one person was cured, now and again; shown through the medium of water (cf. Chrysostom, "Hom. on St. John", 36, 1).
The Sixto-Clementine edition of the Vulgate includes here, as a second part of verse 3 and all of verse 4: "waiting for the moving of the water;  For an angel of the Lord went down at certain seasons into the pool, and troubled the water' whoever stepped in first after the troubling of the water was healed of whatever disease he had." The New Vulgate, however, omits this passage, assigning it to a footnote, because it does not appear in important Greek codexes and papyri, nor in many ancient translations.
14. The man may have come to the temple to thank God for his cure. Jesus goes over to him and reminds him that the health of the soul is more important than physical health.
Our Lord uses holy fear of God as motivation in the struggle against sin: "Sin no more, that nothing worse may befall you". This holy fear is born out of respect for God our Father; it is perfectly compatible with love. Just as children love and respect their parents and try to avoid annoying them partly because they are afraid of being punished, so we should fight against sin firstly because it is an offense against God, but also because we can be punished in this life and, above all, in the next.
16-18. The Law of Moses established the Sabbath as a weekly day of rest. Through keeping the Sabbath the Jews felt they were imitating God, who rested from the work of creation on the seventh day. St. Thomas Aquinas observes that Jesus rejects this strict interpretation: (The Jews), in their desire to imitate God, did nothing on the Sabbath, as if God on that day had ceased absolutely to act. It is true that He rested on the Sabbath from His work of creating new creatures, but He is always continually at work, maintaining them in existence. [...] God is the cause of all things in the sense that He also maintains them in existence; for if for one moment He were to stop exercising His power, at that very moment everything that nature contains would cease to exist" ("Comm. on St. John, in loc.").
"My Father is working still, and I am working": we have already said that God is continually acting. Since the Son acts together with the Father, who with the Holy Spirit are the one and only God, our Lord Jesus Christ, the Son of God, can say that He is always working. These words of Jesus contain an implicit reference to His divinity: the Jews realize this and they want to kill Him because they consider it blasphemous. "We all call God our Father, who is in Heaven (Isaiah 63:16; 64:8). Therefore, they were angry, not at this, that He said God was His Father, but that He said it in quite another way than men. Notice: the Jews understand what Arians do not understand. Arians affirm the Son to be not equal to the Father, and that was why this heresy was driven from the Church. Here, even the blind, even the slayers of Christ, understand the works of Christ" (St. Augustine, "In Ioann. Evang., 17, 16). We call God our Father because through grace we are His adopted children; Jesus calls Him His Father because He is His Son by nature. This is why He says after the Resurrection: "I am ascending to My Father and your Father" (John 20:17), making a clear distinction between the two ways of being a son of God.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.