After the Lord told Noah to go into the ark and to bring seven of each clean animal into the ark, the Lord explained why He told them to enter,

“For after seven more days I will cause it to rain on the earth forty days and forty nights, and I will destroy from the face of the earth all living things that I have made” (Genesis 7.4).

The Lord was not in a rush, but He was patient as He executed His plan.

He had already decided that it would be one hundred twenty years from the time He decided to destroy the world with a flood to the beginning of the flood (Genesis 6.3).

Therefore, seven days before the flood began, Noah and his family needed to get into the ark, and to bring in all the animals and put them into their various places inside, and that would require a great deal of time; evidently it would require seven days, or less than that, perhaps giving the people time to rest between getting all the passengers ready and the beginning of a cataclysmic flood.

Still, it is interesting to see how the Lord works, and how the number seven constantly comes into play.