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.

Whom did Jesus pronounce blessed?
What did Christ indicate as essential to eternal life?
When did David say he would be satisfied?
What endearing title is given the sixth church?
Is this chastening a pleasant experience?
How often did David say he would pray?
Why did the unjust judge answer the widow's prayer?

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