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.

How did Christ suggest that His disciples follow His example in teaching gospel truth?
Why are we admonished to fear God and keep His commandments?
What did the apostles say to the idolaters at Lystra?
What is set forth as the basis for hope and comfort?
What is an evidence of perfection?
What is God's attitude toward the poor?
What peaceful condition will prevail in the earth made new?

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