'Three' in the Bible

The leech has two daughters,“Give, give!”There are three things that are never satisfied,Four that do not say, “It is enough”:

There are three things which are too astounding and unexpectedly wonderful for me,Four which I do not understand:

Under three things the earth is disquieted and quakes,And under four it cannot bear up:

There are three things which are stately in step,Even four which are stately in their stride: