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 loss do those sustain who do not accept Him?
To whom, therefore, should we ascribe glory and honor?
Through what does grace reign unto eternal life?
What precious promise did Jesus make to His disciples shortly before His crucifixion?
What did these four beasts represent?
When were the first of these signs to appear, and what were they to be?
When are the righteous to be recompensed?

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