In Ezekiel 26:11, this signifies the love of learning or intellectual things. (Arcana Coelestia 3727)

In Revelation 6:2, this signifies the love of understanding the Word. (Apocalypse Revealed 298)

In Zechariah 12:4, this signifies that the intellectual should be filled with falsities. (Arcana Coelestia 2383[2])

In general, 'a horse' signifies knowledge or understanding of the Word. In an opposite sense it signifies the understanding of the Word falsified by reasonings, and likewise destroyed from self-derived intelligence. 'A dead horse' signifies no understanding of truth from the Word.

9946. 'And for Aaron's sons' means Divine Truths emanating in the heavens from the Lord's Divine Good. This is clear from the representation of 'Aaron's sons' as Divine Truths emanating from the Lord's Divine Good, dealt with in 9807, in the heavens being meant because that which is Divine and the Lord's in the heavens is what the priestly office of Aaron and his sons represents. Divine Good in the heavens is represented by Aaron's priestly office, and Divine Truth from Divine Good there by that of his sons. The words 'in the heavens' are used because the Lord Himself, being the Sun of heaven, is above the heavens, yet has a presence within the heavens, which is such that it seems as though He Himself were there. The Lord as He is in the heavens - that is, His Divine Good and Divine Truth there - is able to be represented, but not that which is Divine and His above the heavens, because this cannot fall within the range of what human minds or even angelic minds can grasp, since it is infinite. But what is Divine and emanates from it into the heavens is suited to reception there.