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 message of entreaty has God sent to us through His appointed messengers?
Why did the apostle say this duty was so imperative?
Did Jesus ever make use of ordinary means in performing His miracles?
What effect did this dream have upon Daniel?
With what question did Christ meet their false ideas and reasoning regarding Sabbath-keeping?
What will be the third plague?
What above all else shows God's willingness to do this?

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