It's a landmark for a young child to count to 100; it sort of covers all the "ordinary" numbers. One hundred is obviously significant for other groupings: 100 cents is a dollar; 100 yards is a touchdown; 100 years is a century, and the landmark for a very long life. It makes sense, then, that in the Bible, 100 represents fullness or a state of completion, or in some instances simply "much." For instance, people marvel that Abraham had Isaac when he was 100 years old; the number represents the point at which the Lord, when growing up as Jesus, united the human elements of himself with the divine elements and in a sense became "complete.

Donkeys signify things relating to the intelligence of the sensual man; and camels, the things of intelligence in the natural man. (Isaiah 30:6, 7)

In Genesis 12:16, donkeys signify earthly knowledge. (Arcana Coelestia 1486)

In 1 Samuel 9:3, donkeys signify the Lord's preparation for His natural life on Earth. (Arcana Coelestia 2781[5])

In Luke 19:28, 41, a donkey and the foal of an donkey signify the natural man as to good and truth.

(Verweise: Apocalypse Explained 654)