Why is Abraham the first Jew?

I asked my spiritual adviser about this and he said something about Judah and the Hebrews, but I didn’t understand and I feel really stupid for not knowing this solidly like I know the rest of my faith.

Abram made a covenant with God, in which his name was changed to Abraham. That covenant made him the father of a new people, through his son Isaac. For many centuries, God’s chosen people were known as the Israelites (after Isaac’s son, Israel) or Hebrews. When the ten tribes of Israel were dispersed and the remaining Israelites were primarily from the tribe of Judah, then the terms “Jew,” “Jewish,” and “Judaism” began to be used to refer to the chosen people and their religion. (See this article for more information.)

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