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.

In what other statement is the same truth emphasized?
How does godly sorrow for sin manifest itself?
What is inseparable from the experience of justification by faith?
Were the Ten Commandments a distinct and complete law by themselves?
What reply did Moses make to the rulers?
What will He say to those on His right hand?
Why was this to be?

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