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.

To whom is our worship justly due?
How is the love of God supplied to the believer?
When purged from these sins, in what condition is a man, and for what is he prepared?
How futile was all this?
In view of the judgment, what exhortation is given?
How does Joel describe the day of the Lord?
What did Christ tell the rich young man to do?

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