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.

Unto whom will the saints forever ascribe praise?
9. In what words to Peter did Jesus indicate the kind of service a converted person should render to his brethren?
What is the great purpose of Christ in His work of reconciliation?
How many were saved in the ark?
In consequence of this, what value did Christ place upon their worship?
What is predicted of the moral condition of the world in the last days?
How many distinct classes will have a resurrection?

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