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 is Christ to one renewed after God's image?
To what parts of the ancient armour is faith compared?
How does the Spirit witness to our acceptance with God?
Of what were the works of Abraham an evidence?
How willing is God to give to us the Holy Spirit?
What assurance has God given of the judgment?
How will the righteous ever afterward appear?

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