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.

15. When God sent the Ninevites a warning message, how did they show their repentance, and what was the result?
How did persecution affect the preaching of the gospel?
18. What is said of those who live to see the deliverance from modern Babylon, and the restoration of the true gospel?
What did Christ say of worship based upon the commandments of men?
What is Christ's message to the last church?
Why are we exhorted to patience?
In ministering to the needy, whom are we really serving?

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