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.

Why did John write his testimony concerning God's love and purpose in giving Christ?
On what basis is there no possibility of justification for the sinner?
For what purpose is the mystery of the gospel made manifest?
For what is it profitable?
How does God regard those who walk in His law?
6. How did they manifest their displeasure at His healing the man with the withered hand on the Sabbath?
To whom, then, should its observance be rendered?

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