God used the number 400 in a prophecy that He gave to Abraham concerning his seed.
In Genesis chapter 15:13-14, the Bible states:
"13 And he said unto Abram, Know of a surety that thy seed shall be a stranger
in a land that is not theirs, and shall serve them; and they shall afflict them
four hundred years;
14 And also that nation, whom they shall serve, will I judge: and afterward
shall they come out with great substance."
This was a prophecy about Israel being in bondage in the
land of Egypt. IGod promised to bring Israel out of Egypt in the 4th generation.
God did bring them out under the leadership of Moses. The 400 number is an
increase of the number 40 which is used in the Bible as a period for
ordeals.
Thus we have multiple ranges of the number 4:
400 years in bondage in Egypt - and God delivered them in the (4x100)
4th generation - later, they would spend (4x1)
40 years wondering in the desert before entering into the promised land (4x10)
4 - 40 - 400
Note - God also used the number 40 to number Moses life at this time.