After seven days, the rain would start. The rain is the source from which the flood came to be. Here the Lord still spoke generally of rain while Genesis 7:12 speaks of a specific kind of rain—a very heavy rain, a torrential rainfall.
Noah did what the Lord commanded. He prepared everything in time for his family to enter the ark seven days before the flood started. The animals of which the Lord had spoken came to the ark: one pair of the unclean animals, and seven pairs of the clean animals. It gets really busy around the ark. But everyone had their own space. It should also be noted that, in a sense, the Lord brought back the state of paradise. All kinds of animals were present, and they tolerated each other! There was peace and harmony. There were no animals attacking others. It also appeared that the Lord was making sure that the predators could now live without meat for a long time.
When they had been in the ark for seven days, the rain finally came. The flood had started. It was in the 600th year of Noah’s life. The water came with great force over the earth. It was pouring with rain. Water also welled up out of the earth. We read it this way in Genesis 7:11: on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened.
The fountains of the great flood of water bursting open indicates that a great tidal wave from the sea surged over the land. The rain poured down on the earth for forty days and nights without stopping.
4 For in seven days I will send rain on the earth forty days and forty nights, and every living thing that I have made I will blot out from the face of the ground.”