Genesis 4:4-5 ESV And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the Lord had respect unto Abel and to his offering:  But unto Cain and to his offering he had not respect. And Cain was very wroth, and his countenance fell.
To re-enter the true place of worship we have learn over the last 8 studies that...
1. SIN MUST BE DEALT WITH IN GOD'S WAY:
God taught Adam and Eve that sin would have to be dealt with His way before man could re-enter the place of worship. In the Garden of Eden we saw that there is a right way and a wrong to deal with sin.
We will see now that there is a right way and a wrong way to worship. In the life of Adam’s children, Cain and Abel, we will see that not all worship is acceptable to God.
2. NOT ALL THAT WE CALL WORSHIP IS ACCEPTABLE TO GOD:
Somewhere in the Christian arena we have come to believe that God is obligated to accept any act of worship that we choose to bring in any way we choose. But this idea is not in line with the teachings of the Word of God. The Father is not obligated to accept any act of worship that man chooses to bring before Him.
In reading Gen.4:2-5, why do you think that God accepted Abel’s offering but rejected the offering that Cain brought? Could it be that Abel’s sacrifice was an animal and Cain’s was not? Could it be that Abel’s offering was the “firstfruits” and Cain’s was just an offering?
God had already established that there could be no covering of sins or worship without the shedding of blood. Cain wanted worship but he wanted it with the work of his own hands and not the way established by the Father. It is believed that 3 things were wrong with Cain’s worship sacrifice. (1). It was the wrong offering. (2). It was not the firstfruits. (3). It was given from a wrong heart.
This reveals that we cannot worship God any way that we please. The heart of the outward and the inward sacrifice must be right. The outward sacrifice we give to the Lord must be what He asked for. It must come from the right inward sacrifice, a heart with pure motives.
Lest we think that this is just an Old Testament thought or doctrine we need to reread Romans 12:1-2 and see that the word "acceptable" is there. God does not nor will not just accept anything we offer.
Rom 12:1-2(ESV) I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. 2 Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.
Charles Morris. Founder and Senior Pastor of RSI Ministry, RSI School of Ministry, and RSI Publishing L.L.C..