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 do the heavens declare?
What peaceful, happy conditions will prevail in the next world as compared with those of this life?
How, then, did the Lord prove the people (verse 4) whether they would keep His law, or not?
Which day is the Sabbath?
What will He say to those on the left?
What else has He promised to do?
Who is the seed to whom this promise was made?

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