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 advice was given to Timothy while preparing for the gospel ministry?
Why did the apostle say this duty was so imperative?
How came Jesus to live for a time in Egypt?
What is the duty of every child?
How should all Christian parents bring up their children?
How is the conflict between Christ and Satan described?
At His ascension, what assurance was given of Christs return ?

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