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 are the evidences that one has been born of God?
What did Christ's words at Jacob's well lead the woman of Samaria to ask?
What announcement immediately follows the judgment-hour message of Rev. 14: 6,7?
What does God say the Sabbath will be to those who hallow it, or keep it holy?
At Corinth what did he do on the Sabbath days?
10. Under what illustration from nature are the resurrection and the final salvation of the righteous taught?
7. What description does Paul give of the sufferings endured by some of God's people in former ages?

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