Verses with the word obstinate in the Old Testament (2 verses):

Deuteronomy 2:30
But Sihon king of Heshbon would not let us pass by him: for the LORD thy God hardened his spirit, and made his heart obstinate, that he might deliver him into thy hand, as appeareth this day.

Isaiah 48:4
Because I knew that thou art obstinate, and thy neck is an iron sinew, and thy brow brass;