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 cannot the natural man receive the things of the Spirit?
In what promise was a Saviour from sin first revealed?
Where was Christ next taken?
What is the Lord able to do regarding the future?
With what words did Daniel begin the interpretation of the dream?
What will constitute the second plague?
How did man lose his dominion?

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