'Forty' represents completeness because 'four' and 'ten' both mean what is complete. Forty is the product of four and ten. Compound numbers have a meaning similar to the simple numbers which compose them, and all numbers in the Word represent spiritual realities.

(Reference: Arcana Coelestia 9437; Exodus 24:18)

127. Internal Meaning of Ezekiel, Chapter 4

Representation of the perverted church in the church. (2)

1-2 He should represent the falsities of the church, and the church besieged by them. (2)

3 He should represent the hardness of their heart, from which it is that they have no fear; (2)

4-8 he should also represent the church besieged by falsities of evil and evils of falsity. (2)

9-16 He should represent the falsification and adulteration of the sense of the letter of the Word, (2)

17 by which everything of the church has perished. (2, 3)