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.

2348. This shows that human beings after the flood are able to retain all their own life, and to feel it as their own, although neither the life nor the sensation are theirs, but only appear as theirs, differently from those who were before the flood. So the rainbow became a sign, and it was added that there would never cease being winter, summer, spring [Gen. 8:22], which are changes portraying comparable things on the inward level of meaning. 1748, 17 June.