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.

What change is wrought by beholding Jesus?
How complete should this obedience be?
What is the mark of a true friend?
Why was it necessary for Christ to go away?
How may we be freed from the guilt of our sins, or our transgressions of God's law?
What becomes of the living wicked when Christ comes?
What experience followed this trust in Jesus?

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