Aaron's Seven Days of Mourning and God Mourning Before the Flood

"And it came to pass on the eighth day, etc." (Leviticus 9:1). This is what Scripture says: "Whoever keeps a commandment will know no evil thing" (Ecclesiastes 8:5). Who was this? Aaron, of whom it is said: "And from the entrance of the Tent of Meeting you shall not go out for seven days" (Leviticus 8:33), and "At the entrance of the Tent of Meeting you shall remain day and night for seven days" (Leviticus 8:35). Moses said to them: Observe mourning for seven days. "And you shall keep the charge of the LORD" (Leviticus 8:35). Moses said to them: Keep the charge of the LORD, for so did the Holy One, blessed be He, observe seven days of mourning before He brought the Flood. And from where do we know that He mourned? As it is said: "And the LORD regretted that He had made man on the earth, [and He grieved in His heart]" (Genesis 6:6). "And He grieved" means nothing other than mourning, for so it says regarding David: "[And the victory on that day was turned into mourning for all the people, for the people heard it said on that day:] The king is grieving over his son" (2 Samuel 19:3). And likewise Ezra said to Israel, at the time when they were weeping each man to his brother and each man to his son: "Go, eat the fat and drink the sweet, etc., and do not grieve, for the joy of the LORD is your strength" (Nehemiah 8:10). Therefore it is said: "And He grieved in His heart." At that time the Holy One, blessed be He, observed the seven days of mourning before He brought the Flood, as it is said: "And it came to pass after the seven days [that the waters of the Flood were upon the earth]" (Genesis 7:10). And so Moses said to Aaron the priest and to his sons: Just as the Holy One, blessed be He, mourned over His world before He brought the Flood, so observe the mourning before it touches you. And they observed it, but they did not know for what they were observing. Why? "Whoever keeps a commandment will know no evil thing, and a wise heart knows the time and the judgment" (Ecclesiastes 8:5).