The first thing we learn about the two sons of Adam and Eve is that they brought offerings to God. Genesis 4:3 tells us about Cain’s offering. It says, “In the course of time Cain brought to the Lord an offering of the fruit of the ground….” The opening phrase, “in the course of time,” has opened some interesting dialogue. Mike Boling says, “Perhaps as suggested by Adam Clarke, the process of time ‘means the Sabbath’, on which Adam and his family undoubtedly offered oblations to God, as the Divine worship was certainly instituted, and no doubt the Sabbath properly observed in that family. This worship was, in its original institution, very simple. It appears to have consisted of two parts.” According to Mike, the two parts are thanksgiving and piacular sacrifices. He defines “piacular” for me. Thank you, Mike. He says, “For those not familiar with the word piacular, it means ‘making or requiring atonement’.” This might help us understand why Cain’s offering was unacceptable.
Yet, there are no recorded instructions from God or Adam and Eve regarding the nature of sacrifices. Why isn’t there more detail given? To answer this, Mason Wheeler spoke about this in a web blog. He wrote, “Storytellers tend to explain unfamiliar concepts and not waste time explaining familiar ones, so it’s reasonable to infer that Adam and his family were under a commandment from God to offer sacrifices in a similar, if not identical, manner to the rules about sacrifices in the Law of Moses. Beyond that, the Bible is unfortunately silent.”[1] It is not silent, however. We have the instance of God’s sacrificing lambs, or a lamb, to make clothing for Adam and Eve to replace their inadequate fig leaves.
It might have been at the time of God’s slayings the lamb to make clothes for Adam and Eve that God gave instructions regarding worship. The best we can do is assume that such instruction happened. It seems as MacArthur points out, that this is reasonable. He says, “Apparently God had designated a special time for sacrificing because “in the course of time” (v. 3) literally means, “at the end of days”—at the end of a certain period of time. Additionally, He initiated a particular pattern for worship and sacrifices. Otherwise Cain and Abel would have known nothing about how it was to be done.”[2] As we look back at this from the perspective we have of the Old Testament sacrificial system and the “Lamb of God that takes away the sin of the world” we see that a sacrifice is something required of God. It’s all looking forward to the ultimate sacrifice that will be offered “once and for all” for all mankind. Our righteousness and sanctification is now an accomplished face according to Hebrews 10:10. It says, “And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.”
[1] https://christianity.stackexchange.com/questions/572/how-did-cain-and-abel-know-to-offer-sacrifices-before-the-law-of-moses
[2] MacArthur, John F., Jr. 1993. Drawing Near—Daily Readings for a Deeper Faith. Wheaton, IL: Crossway Books.