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 we close our ears to truth, and remain innocent before God?
What were these gifts that Christ gave to men?
What power mentioned in the thirteenth chapter of Revelation is to enforce this mark?
What promise is made to those who look for Him?
Upon what one fact does Paul base the Christian hope?
What will be the final doom of Satan and his angels?
What did David ask God to teach him?

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