Quote from : The Meaning of Hebrew Letters: A Hebrew Language Program for Christians Book

We should expect nothing less from the language that was originally given by God, to His human family. Hebrew was the method that God chose for mankind to speak to Him, and Him to them. Adam spoke Hebrew—and your Bible confirms this. Everyone who got off the ark spoke one language—Hebrew. Even Abraham spoke Hebrew. Where did Abraham learn to speak Hebrew? Abraham was descended from Noah’s son, Shem. (Ge 11:10-26) Shem’s household was not affected by the later confusion of languages, at Babel. (Ge 11:5-9) To the contrary, Shem was blessed while the rest of Babel was cursed. (Ge 9:26) That is how Abraham retained Hebrew, despite residing in Babylon. So, Shem’s language can be traced back to Adam. (Ge 11:1) And, Shem (Noah’s son) was still alive when Jacob and Esau was 30 years of age. Obviously, Hebrew (the original language) was clearly spoken by Jacob’s sons. (Ge 14:13)