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.

In what other statement is the same truth emphasized?
By what are men sanctified?
Following one of His parables, what did Christ say?
What is said of the poor but wise child?
What, more than all else, proves the perpetuity and immutability of the law of God?
To what length will this effort to enforce the worship of the image of the beast be carried?
What does the historian say of this legislation?

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