332. And the sun became as black as sackcloth of hair, and the moon became like blood. This symbolically means that all goodness of love was adulterated in those people, and every truth of faith falsified.
The sun symbolizes the Lord in respect to His Divine love, and thus the goodness of love emanating from Him; and in an opposite sense it symbolizes the Lord's Divinity denied, and thus the goodness of love adulterated. See no. 53 above. And because the sun symbolizes the goodness of love, therefore the moon symbolizes the truth of faith. For the sun has a reddish glow owing to its fire, while the moon glows white from the light radiating from the sun, and fire symbolizes the goodness of love, while light symbolizes the truth arising from that goodness. Regarding the moon, see also the places cited above in no. 53.
The sun is said to have become as black as sackcloth of hair because good adulterated is, in itself, evil, and evil is black.
The moon is said to have become like blood because blood symbolizes Divine truth, and in an opposite sense Divine truth falsified. See nos. 379, 684 below.
The sun and moon are described in almost the same way in Joel:
The sun shall be turned into darkness, and the moon into blood, before the coming of the great and terrible day of Jehovah. (Joel 2:31)