7616. 'And Pharaoh's heart was made unyielding' means that evil was the cause of their obstinate behaviour. This is clear from the meaning of 'the heart being made unyielding' as behaving obstinately, dealt with immediately above in 7615. Where it says that he made his heart stubborn. The difference is that 'making the heart stubborn' is caused by falsity, whereas 'making the heart unyielding' is caused by evil.