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.

What is sin declared to be?
What would make the death of Christ in vain?
What has Christ brought to light through the gospel?
What is set forth as the basis for hope and comfort?
What other event is mentioned under this seal?
What does Paul say of their number?
To whom did Jesus first send the twelve disciples?

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