Jn. 8:57. Then the Jews said to Him: You are not yet fifty years old – and You have seen Abraham?
The Jews, being unable to rise to the meaning of His words, instead of asking and learning about which day He speaks of that Abraham saw, mock Him even more, as though He were saying something senseless. "You are not yet fifty years old," they say, "and You have seen Abraham?" They said this, thinking that the Lord was close to fifty years old, when in fact He was about thirty-three years old.
Why did they not say "You are not yet forty years old," but "fifty"? It would be superfluous even to ask about this. Perhaps they mentioned fifty years without any definite thought. However, some say that they spoke this way because the fiftieth year was especially honored among them, that is, the jubilee year, in which slaves were set free, buyers relinquished their acquisitions, and they did everything else that pertained to that honor.
Jn. 8:58. Jesus said to them: Truly, truly, I say to you: before Abraham was, I am.
What then does the Lord say? "Before Abraham was, I am." See, He did not say "before Abraham was, I was," but "I am." For this expression "am" is more proper to God, because it signifies continuous and eternal existence. So too His Father in the Old Testament said of Himself: "I am He Who Is" (Ex. 3:14). Of Abraham, as one subject to corruption, He fittingly said "was." For that which received existence is also subject to dissolution. But the word "am" points to freedom from all corruption and to divine eternity.
Jn. 8:59. Then they took up stones to cast at Him; but Jesus hid Himself and went out of the temple, passing through the midst of them, and so passed by.
Therefore they too accepted this saying as befitting God alone, took it for blasphemy, and picked up stones against Him. But He again hides Himself with humility, so as not to die before the time appointed for His death.
How then does He hide? He did not conceal Himself in a corner of the temple, did not run off into a house, did not lean against a wall or behind a pillar, but by divine power He made Himself invisible to the plotters, even though He went out through the midst of them. "And passed by," that is, He went along simply, for a certain time.
Look, if you will, how He fulfilled everything on His part: He sufficiently taught them both about Himself and about the Father, and pointed out true nobility and freedom in freedom from sins; He explained that the only shameful slavery is slavery to sin — and in general He omitted nothing that was needed. But they throw stones at Him. This is precisely why He leaves them, as people no longer capable of correction.
Note that the stones are thrown by those about whom the Evangelist said that they believed in Him (Jn. 8:30–31). This means their faith was not faith, but a kind of temporary and lukewarm disposition toward the words of Christ.