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 encouragement is held out as an aid in attaining this experience?
What charge did Jesus bring against the Pharisees?
And how may we know that we love the brethren?
And what is indicated as the lawful use of the law?
When the sign appeared, how suddenly were they to flee?
What is the last enemy to be destroyed?
What will cause the Christian to grow?

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