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.

2643. 'Who would have said to Abraham, Sarah will suckle sons?' means that by His own power the Lord implanted the Human within the Divine. This is clear from the representation of 'Abraham' and also of 'Sarah', and from the meaning of 'suckling', and of 'sons'. It has been shown already that 'Abraham' represents Divine Good and 'Sarah' Divine Truth. 'Milk' means that which is spiritual from a celestial origin, that is, truth deriving from good, see 2184, so that 'suckling' means implanting that truth; And 'sons' means truths, here truths that exist in the Rational, as is clear from the meaning of 'sons', 489-491, 533. The reason why in the internal sense the words under consideration mean that the Lord by His own power implanted the Human within the Divine is that Divine Truth is one and the same as the Divine Human, and when in reference to this it is said 'to suckle sons for Abraham' the meaning is that He implanted the Human within the Divine; and as it was the Human He implanted, He did so by His own power. But scarcely any clearer and more intelligible explanation of these matters is possible. To say more would obscure still further what is meant; for these are Divine matters, which can be presented to angels alone by means of celestial and spiritual things. If presented to men in some more exalted manner those matters would fall into the material and bodily ideas which men possess.

[2] What is more, it should be recognized that it is the nature of the Lord's Divine Rational when it was first born that is being described by these words, 'God has made laughter for me; everyone that hears will laugh for me; and she said, Who would have said to Abraham, Sarah will suckle sons?' For this was in keeping with an ancient custom that when an infant was born it was given a name which served to mean the state; and at the same time a description of that state was added, as when Cain was born to Eve and Adam, Genesis 4:1, and when Seth was born to the same, Genesis 4:25; and as when Noah was born to Lamech, Genesis 5:29, Esau and Jacob to Isaac, Genesis 25:25-26, the twelve sons to Jacob, Genesis 29:32-35; 30:6, 8, 11, 13, 18, 20, 24; 35:18, Perez and Zerah to Tamar, Genesis 38:29-30, Manasseh and Ephraim to Joseph, Genesis 41:51-52, and Gershom and Eliezer to Moses, Exodus 2:22; 18:4. What all these represent, and what they mean in the internal sense, was embodied in the descriptions added to the names that were given. The same is the case here with what Isaac represents and means. What this name embodies is evident to some small extent from this brief explanation that has been given, but deeper arcana are nevertheless concealed there since they are Divine matters, which no sentences or phrases can be formed to express.