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 other experience is associated with conversion?
In what way are both Jews and Gentiles to be justified?
By what method of reasoning did Christ justify acts of mercy on the Sabbath day?
What was Satan's design in thus persecuting the church?
How is this great and dreadful day described in this same prophecy?
By what title does the Psalmist address God?
From what ills will the saints he for ever delivered?

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