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.

Can anything separate the true child of God from the love of God?
To whom are sinners brought by conversion?
Through what was the original creation wrought?
For what is all Scripture profitable?
What proves that the law is an undivided whole?
What definite period is mentioned under this trumpet?
What will the righteous do upon rising from the grave?

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