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.

To whom will the gates of the heavenly city finally be opened?
By what did Peter, on the day of Pentecost, say that Christ had been approved by God?
Because of this, what is Christ able to do?
Did Christ have anything to do with creation and the making of the Sabbath?
How did Jesus answer them?
But are not the righteous dead in heaven?
What universal chorus of praise will then be heard?

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