Charles Ellicott Commentary Leviticus 16:1

"And Jehovah spake unto Moses, after the death of the two sons of Aaron, when they drew near before Jehovah, and died;" — Leviticus 16:1 (ASV)

And the Lord spake unto Moses. —As the observance of the minute regulations given in the preceding chapters about the daily sacrifices and purifications would necessarily be tainted with many imperfections and shortcomings, both on the part of the mediating priests and the offering laity, a general day of atonement is here instituted, when priest and people are both to obtain atonement once a year for the sins which were mixed up even with their sacred worship.

The day of atonement enacted in this chapter is therefore an appropriate conclusion of the laws of purification in the preceding chapters. It is an annual supplement and completion of all the ordinances which were daily practiced, and the design of which was to obtain atonement and reconciliation.

After the death of the two sons of Aaron. —That is, after Nadab and Abihu, his two eldest sons, had died because they had presumptuously entered the sanctuary in a profane manner and at an irregular time (See Leviticus 10:1-2.).