Arcana Coelestia #6257
6257. 'Because of old age' means because he was in the final phase of his representation. This is clear from the meaning of 'old age' as a new state of representation, dealt with in 3254, thus the final phase of a former one.
Genesis 48:3
3
Jacob said to Joseph, "God Almighty appeared to me at Luz in the land of Canaan, and blessed me,