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.

For what purpose were the Scriptures written?
What ordinance is closely associated with believing the gospel ?
What is inseparable from the experience of justification by faith?
What great truth therefore follows?
What was the Comforter to do when He came?
How was this covenant then confirmed and dedicated?
What description does the prophet Jeremiah give of the earth during this time?

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