How early was this sacrificial system known?

Answer

"By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he
was righteous, God testifying of his gifts." Heb. 11: 4. See Gen. 4: 3-5; 8: 20.

Of what kind of doctrines should we beware?
How highly does God regard obedience?
Of what is the Sabbath commandment a part?
With what are we to comfort one another?
But are not the righteous dead in heaven?
In the judgment, how many angels minister before God?
Does He afflict to leave the one chastened in despair?

Questions & Answers are from the book Bible Readings for the Home Circle