It was a memorial for the Israelites, that no outsider who is not a descendant of Aaron should approach to burn incense before the Lord, that he might not become like Korah and his company – just as the Lord had spoken by the authority of Moses.
By faith Abel offered God a greater sacrifice than Cain, and through his faith he was commended as righteous, because God commended him for his offerings. And through his faith he still speaks, though he is dead.
He has no need to do every day what those priests do, to offer sacrifices first for their own sins and then for the sins of the people, since he did this in offering himself once for all.