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 freely was the Holy Spirit bestowed upon Him?
Where were the Ten Commandments placed?
What reason is given for making the new covenant?
What has He commanded men to observe in memory of this great work?
What part will the angels have in this event?
What becomes of man's thoughts at death?
5. Before their entrance into Canaan, what instruction did Moses give Israel concerning these things?

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