there is no record of instructions given to Adam, to Eve, to Abel or to Cain regarding offerings or how to approach Him. i think we should let Genesis 1-3 inform us about Genesis 4.
the record introducing the narrative of Genesis 4 is Genesis 3:21, that the LORD made tunics of hide for Adam & Eve.
it is much more natural to presume that what they are doing is a voluntary commemoration of this than to imagine that God commanded them a detailed liturgical code that He doesn't bother recording in the book -- are they making tunics for themselves? what do they wear? what does Abel do with the hide from the sheep he slaughtered? God tells Cain "if you do what is right" - how does what is actually written in Genesis 3 inform him of what is right and what is wrong? God removes the coverings they made for themselves and makes coverings for them Himself. is Cain wearing fig leaves? if Abel's gift showed faith and Cain's showed unbelief, how did it show unbelief? it's not like he brought nothing at all - and seeing that Abel was a keeper of sheep, it's not like he didn't offer something from his own labor. just how evil is Cain's offering?
the record introducing the narrative of Genesis 4 is Genesis 3:21, that the LORD made tunics of hide for Adam & Eve.
it is much more natural to presume that what they are doing is a voluntary commemoration of this than to imagine that God commanded them a detailed liturgical code that He doesn't bother recording in the book -- are they making tunics for themselves? what do they wear? what does Abel do with the hide from the sheep he slaughtered? God tells Cain "if you do what is right" - how does what is actually written in Genesis 3 inform him of what is right and what is wrong? God removes the coverings they made for themselves and makes coverings for them Himself. is Cain wearing fig leaves? if Abel's gift showed faith and Cain's showed unbelief, how did it show unbelief? it's not like he brought nothing at all - and seeing that Abel was a keeper of sheep, it's not like he didn't offer something from his own labor. just how evil is Cain's offering?
God gave him a chance to correct it. He did not and this gave Satan an opportunity to slay the promised seed, Abel, by using Cain. God replaced Abel with Seth and continued the seed line on through Genesis 5 to Noah.
Hebrews 11:4 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: and by it he being dead yet speaketh.