Gemara distinguished between the mourning of God and people: People, who do not know what will happen until it happens, do not mourn until the deceased dies. But God, who knows what will happen in the future, mourned for the world before its destruction. The Gemara noted, however, that there are those who say that the seven days before the Flood were days of mourning for Methuselah (who died just before the Flood). Similarly, reading in that "it came to pass on the eighth day," a Midrash recounted how Moses told Aaron in "you shall not go out from the door of the tent of meeting seven days." The Midrash interpreted this to mean that Moses thereby told Aaron and his sons to observe the laws of mourning for seven days, before those laws would affect them. Moses told them in that they were to "keep the charge of the Lord," for so God had kept seven days of mourning before God brought the Flood, as reports, "And it came to pass after the seven days, that the waters of the Flood were upon the earth." The Midrash deduced that God was mourning by noting that reports, "And it repented the Lord that He had made man on the earth, and it grieved Him (, vayitatzeiv) at His heart." And uses the same word to express mourning when it says, "The king grieves (, ne'etzav) for his son." After God told Moses in "And there I will meet with the children of Israel; and [the Tabernacle] shall be sanctified by My glory," Moses administered the service for seven days in fear, fearing that God would strike him down. And it was for that reason that Moses told Aaron to observe the laws of mourning. When Aaron asked Moses why, Moses replied (in the words of ) "so I am commanded." Then, as reported in God struck Nadab and Abihu instead. And thus in Moses told Aaron that he finally understood, "This is what the Lord meant when He said: ‘Through those near to Me I show Myself holy, and gain glory before all the people.'" In medieval Jewish interpretation This and the preceding parashah, Vayikra, are discussed in these medieval Jewish sources: Leviticus chapters 1–7 Maimonides and Nachmanides differed about the reason for the sacrificial system. Maimonides wrote that the reason for the offerings was because when the Israelites lived