37. As for the statement that 'the lights will be for signs, and for set times, and for days, and for years', this contains more arcana than can be presented at this point, though no arcanum at all is visible in the sense of the letter. For now only this can be said: Change in spiritual and celestial things takes place both on general and on particular scales, and is comparable to changes that take place through the day and through the year. Changes through the day are from morning to midday, from then on to evening, and through the night to the morning. Changes in the year similar, from spring to summer, from then on to autumn, and through winter to spring. These bring changes in temperature and amount of daylight, and so in the fertility of the earth. Compared to such changes are the changes that take place in spiritual and celestial things. Life without changes and variations would lead to sameness, and so no life at all. Good and truth would not be recognized and identified, let alone perceived. In the Prophets such changes are called 'ordinances', as in Jeremiah,

[Thus] said Jehovah who gives the sun for light by day and the ordinances of the moon and of the stars for light by night, These ordinances will not depart from before Me. Jeremiah 31:35-36.

And in the same prophet,

Thus said Jehovah, If I have not established My covenant of day and night, the ordinances of heaven and earth . . . Jeremiah 33:25.

But these things will in the Lord's Divine mercy be dealt with at Genesis 8:12.

2021. 'For an eternal covenant' means conjunction with these people. This is clear from the meaning of 'a covenant' as conjunction, dealt with already in 665, 666, 1023, 1038; and that this conjunction is with those called 'the seed' is clear from the fact of its coming immediately after a reference to that 'seed', and of its being a second mention in this verse of a covenant. Thus the first mention of 'a covenant' has reference to the union of Jehovah with the Human Essence, and the second to the conjunction with those who are 'the seed'. To allow a clearer idea of the union of the Lord's Divine Essence with the Human Essence and of the conjunction of the Lord with the human race by means of the faith that inheres in charity, let the term union here and from now on be used to describe the first of these, and conjunction the second. Indeed the bond between the Lord's Divine Essence and Human Essence really was a union, but that between the Lord and the human race by means of the faith that inheres in charity is conjunction. From this it is clear that because Jehovah or the Lord is Life, His Human Essence became Life as well, as shown above. It was a union of life with life. Man however is not life but a recipient of life, as also shown already. When life flows into a recipient of life conjunction takes place, for life accommodates itself to the recipient as active does to passive or as that which in itself is living does to that which in itself is dead but made living from that which in itself is living. In the case of the principal and the instrumental, as they are called, they do indeed seem to have been joined together to exist as one. Nevertheless they are not one, for each exists by itself. Man does not live of himself, but the Lord in His mercy links him to Himself and in so doing causes him to live for ever. And because the Lord and man are distinct and separate from each other the term conjunction is used.