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.

For what did David pray?
When was the little horn to arise?
While in this condition, how much does one know about those he has left behind?
What reason did Paul give for glorying in tribulations?
How does the Lord regard kindness shown to the poor?
Upon whom was the name Israel first bestowed?
How readily will their wants be supplied?

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