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 is the only unpardonable sin?
What is one evidence of this change from death to life?
How are those described who accept this message?
What shameful treatment did Christ receive from the soldiers?
What immediately followed this complete apostasy?
What definite period is mentioned under this trumpet?
What did David say with reference to his being afflicted?

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