Today, Saint John places us before Jesus' revelation in the Temple. Our Savior reveals something unknown to the Jews: that Abraham looked forward and rejoiced when he saw Jesus' day. They all knew God had made a promise to Abraham, by assuring him of great promises of salvation for his seed. However, they were unaware of how far God's light could reach. Christ reveals them that Abraham did see the Messiah in the day of Yahweh, which Jesus calls my day.
In this revelation, Jesus appears as having God's eternal vision. But, above all, He appears as someone preexistent and present in Abraham's time. Later, in the heat of the discussion, when the Jews said to Jesus that He is not yet fifty years old, He tells them: «Truly, I say to you, before Abraham was, I am» (Jn 8:58). This is a notorious statement of his divinity, which they could perfectly understand, and which they could have also believed, had they better known the Father. The expression “I am” is part of the holy tetragram Yahweh revealed to Moses in mount Sinai.
Christianism is much more than a collection of high moral norms, as can be perfect love, or even, forgiveness. Christianism is faith in one person. Jesus Christ is True God and True Man. «Perfect God and Perfect Man», says the Athanasian Symbol. Saint Hilary of Poitiers writes in a beautiful prayer: «Give us, therefore, a way to express ourselves in an adequate and dignified manner, to enlighten our intelligence, and make also our words to express our faith, that is, that we, who, through the prophets and the Apostles, had come to know You God Father and the unique Lord Jesus Christ, may also celebrate You as our God, in which there is no unicity of person and confess your Son, in everything equal to You».