3492. 'So it was, that Isaac was old' means when the state was reached. This is clear from the meaning of 'growing old' as the arrival and presence of a new state; for 'old age' in the Word means both the casting aside of the previous state and the assumption of the new one. The reason it has these two meanings is that old age is the final stage of life, when bodily things start to be cast aside together with the loves which belong to the preceding stage, and so when interior things start to be enlightened; for once bodily things have been removed interior things are enlightened. And a further reason for the two meanings is that angels, who perceive spiritually the things that are in the Word, no longer have the concept of old age but instead the concept of new life. Thus by Isaac's being old they perceive that the state was reached, that is to say, when the Divine Rational, represented by Isaac, desired the Natural which corresponded to itself, that is, that the Natural too should be Divine.
(References: Genesis 27:1)