Arcana Coelestia # 8086
8086. 'That Jehovah killed all the firstborn in the land of Egypt' means that all governed by faith separated from charity were damned. This is clear from the meaning of 'the firstborn of Egypt' as faith separated from charity, dealt with in 7039, 7797; as for the death of the firstborn, that it means the damnation of those who are governed by that faith and lead a life of evil, see 7766, 7778.
Arcana Coelestia # 7797
7797. 'And Jehovah made Pharaoh's heart unyielding' means that they remained obstinate. This is clear from the meaning of 'making the heart unyielding' as remaining obstinate, dealt with in 7272, 7300, 7305. The fact that Jehovah does not make the heart unyielding or do anything bad, even though it is attributed to Him in the literal sense of the Word, see 7533, 7631, 7643.