The 13th century Biblical commentator, Hizkuni, explains that Avram (he was not yet called Abraham) had already left his homeland Ur of the Kasdim and was living in Haran. Therefore he was told to leave his land- Haran, and not to go back to his birthplace, Ur, AND to leave his father’s house, and to go where G-d would guide him.
Quite a journey! Leave where you are, don’t go back to where you were, and separate yourself from your parents’ home. Go- and G-d will show you the way.
