Question: Why were the Jews offended when Jesus said, “Before Abraham was, I am”?
Answer: “I am” is a term Jehovah used to identify Himself to Moses, as recorded in Exodus 3:14. So when Jesus said, “I am,” He identified Himself as Jehovah, the God of the Old Testament. The Jews considered this blasphemy, and under the law of Moses, the penalty was death by stoning.
56 Your father (ancestor) Abraham rejoiced to see my day (saw my day in vision): and he saw it, and was glad.
57 Then said the Jews unto him, Thou art not yet fifty years old, and hast thou seen Abraham? (They have missed the point.)
58 Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am. (I am the God who appeared to Abraham).
Note: “I am” in verse 58 above is usually written “I AM,” used here in the Greek, is identical with the Septuagint usage in Exodus 3:14, which identifies Jehovah, the God of the Old Testament. Because the Jews finally understand clearly who Jesus is claiming to be, they are furious with him.
14 And God said unto Moses, I Am That I Am: and he said, Thus shalt thou say unto the children of Israel, I Am hath sent me unto you.
* * * * *
“This is as blunt and pointed an affirmation of divinity as any person has or could make. ‘Before Abraham was I Jehovah.’ That is, ‘I am God Almighty, the Great I AM. I am the self-existent, Eternal One. I am the God of your fathers. My name is: I AM THAT I AM’” (Bruce R. McConkie, Doctrinal New Testament Commentary, 3 vols. [1965–73], 1:464).
By early post-biblical times, the Hebrew name for Jehovah (usually represented as Yahweh in literature) was considered too sacred to be pronounced. For this reason, except for a few exceptions (see Exodus 6:3; Psalm 83:18; Isaiah 12:2; 26:4), the translators of the King James Version of the Bible rendered the word Jehovah as LORD (in all capital letters). In modern Judaism, it is replaced with the word Adonai, which means “Lord.”
Source: Come, Follow Me–For Individuals and Families, p. 67; The New Testament Made Easier, Part 1, Volume 2, by David J. Ridges, 289; Jesus Christ and the Everlasting Gospel Teacher Manual, Lesson 5: Jesus Christ Was Jehovah of the Old Testament.