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.

Through what does grace reign unto eternal life?
For what did Christ reprove the Pharisees?
How, then, did the Lord prove the people (verse 4) whether they would keep His law, or not?
18. Knowing that the unbelieving Jews would still cling to their false ideas respecting the Sabbath, pray?
On what day did Paul and his companions preach to the devout women at Phillippi?
What was the color of the symbol under the third seal?
What were these martyrs represented as doing?

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