Genesis 7:4

"For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living thing that I have made will I destroy from off the face of the ground."

Two things of special interest here are the use of the number "forty," and the destruction of animals, which may not be considered sinful, along with the punishment of human wickedness. Regarding the first of these, Unger pointed out that "forty" appears in both O.T. and N.T. as "the sacred number of trial and patience,"[3] there being many examples of it: Jesus' fasting for forty days, the children of Israel wandering in the wilderness for forty years, etc.

Regarding the second, Jamieson pointed out that such was necessary in order to preserve the ecological balance on the earth.[4] At a time when the human family was being reduced so drastically in numbers, the unlimited proliferation of the lower creation would have become a threat to the lives of men. In addition to this, God's punishment usually extended beyond the strict boundaries of the offense. Thus, Achan was not only destroyed, but his house also (Joshua 7:24f).