These seven days of retirement were assigned to Aaron and his sons not only as a preparation for their regular service, they had another significance also. God, before bringing the flood upon the earth, observed the seven days preceding as a week of mourning, and in the same way He bade Aaron and his sons live in absolute retirement for a week, as is the duty of mourners, for a heavy loss awaited them-the death of Nadab and Abihu, which took place on the joyous day of their dedication.
The first day of Nisan was an eventful day, "a day that was distinguished by ten crowns." It was the day on which the princes of the tribes began to bring their offerings; it was the first day on which Shekinah came to dwell among Israel; the first day on which sacrifice on any but the appointed place was forbidden; the first day on which priests bestowed their blessing upon Israel; the first day for regular sacrificial service; the first day on which the priests partook of certain portions of the offering; the first day on which the heavenly fire was seen on the altar; it was besides the first day of the week, a Sunday, the first day of the first month of the year.