It has often been said that Jesus never claimed that He was God and that this was just something that later Christian writers decided, that it wasn't really a foundational belief of the followers of Jesus. Today's gospel passage is a direct contradiction to that claim. According to the sources that we have - gospels and historical texts from that time period - Jesus never stood up and said the phrase "I am God." However, He did utter many phrases that the people of the day would have taken to mean just that.
In the midst of this ordinary dispute about following Abraham, the Jews are shocked to hear Jesus' claim to have seen Abraham. In reaction to this apparently foolish claim, they mock the Lord and point out that He is still just a veritable youth. Here the Lord responds: "Before Abraham came to be, I AM." It seems an odd statement in English, but 'I AM' was the name that the Jews new God by. In this simple exchange Jesus acknowledges the fact that although He is a man of only 30 years of age, but that He is also God. We can see that the Jewish people clearly understand that Jesus essentially just said "I am God" because they pick up stones to stone him to death, an appropriate punishment for blasphemy. Interesting, eh? :)