What Does Genesis 7:12 Mean?

And rain fell upon the earth forty days and forty nights. The forty-day duration of the rainfall is the most well-known feature of the flood account and the figure that has given the number forty its scriptural weight as a period of sustained testing or transformation. Israel will spend forty years in the wilderness before entering the land; Moses will be forty days on the mountain receiving the law; Jesus will be forty days in the desert before beginning his public ministry. In each case, the period represents a complete cycle of trial that ends in a fundamental change of state.

Here, the forty days of continuous rain accomplished the erasure of the old world. It was long enough to leave no possibility of the waters subsiding on their own, long enough to cover even the highest mountains, as the narrative will describe. The duration was not chosen to be dramatic but to be sufficient. God was not destroying for its own sake but clearing the ground of what the creation account called "very good" but which human rebellion had converted into something characterized by violence and corruption.

The family inside the ark endured forty days of the sound of rain on wood and water, an unceasing sign that the world they had known was ending. There is no record of their conversations during this period, but the silence of the text on that point is itself revealing. They had entered when commanded, they were sealed in by God's own hand, and the rest was beyond their control. All they could do was wait in the dark while God's judgment did what it had announced it would do.