Lev. 10: 4-20, after the deaths

Aaron would never forget this day. How could he? The first day of his duties as high priest. And the day his two eldest sons were killed by God for their actions. Aaron must have been on emotional overload. And his other sons -- forbidden to leave the Temple area, even to carry the bodies of their brothers outside the camp. Other relatives had to do it.

We read in the New Testament
Another disciple said to him, "Lord, first let me go and bury my father."
But Jesus told him, "Follow me, and let the dead bury their own dead."

and although what was going on the New Testament with Jesus was a different situation, the principle is the same. God is first. Always.

Aaron and his two remaining sons are forbidden to mourn. This meant they were forbidden to show mourning publicly with the unkempt hair, torn clothes, and ashes. They had to be priests of the Lord first and although others could mourn, their job was to follow through in serving the Lord. They had been anointed: "The Lord's anointing oil is on you."

In verses 8-10, the Lord Himself gives Aaron three commands:
1. No wine or other fermented drink when going into the Tent of Meeting. Consequences for disobedience? Death.
2. They must distinguish between holy and common; clean and unclean
3. It is their responsibility to teach the people of Israel the decrees of the Lord as given through Moses.

And then Moses commands Aaron and his two living sons to continue their sacrificial duties in the Tent of Meeting. And they do.

But Aaron cannot eat. ...such things as this have happened to me...

Moses accepts this.

But Aaron will never forget this day. And the two remaining brothers will always know how serious the Lord is about His call to service. One does not make light of it. One does not disobey.