Charles Ellicott Commentary Genesis 36:39

"And Baal-hanan the son of Achbor died, and Hadar reigned in his stead: and the name of his city was Pau; and his wife`s name was Mehetabel, the daughter of Matred, the daughter of Me-zahab." — Genesis 36:39 (ASV)

Hadar. —He is more correctly called Hadad in the Samaritan text here, and in the Hebrew also in 1 Chronicles 1:50. The two letters r and d are in Hebrew so much alike, that they are repeatedly confused with one another. As we have already observed (see Note on Genesis 36:1) he was probably alive when this catalogue of kings was drawn up.