What does Genesis 4:5 mean?
The previous verses revealed that the brothers Cain and Abel both had a relationship with God. Both brought Him offerings from their respective areas of work. Cain brought crops from the ground which he worked as a farmer. Abel, a keeper of sheep, brought fat portions from a slaughtered firstborn lamb. Though this part of Scripture gives no specific reasons why, God looks with favor on Abel and his offering.Also without much detail, this verse tells us God had no regard for Cain and his offering. Unless the brothers had been told to bring animal sacrifices, God's response may seem unfair to us at first. Later in this book, God will be clear in requiring animal sacrifices from His people. Had He been clear with Cain about what He preferred? Was Cain offering something less than his "first fruits," in comparison to Abel? We don't know.
It seems more likely that God rejected Cain's offering because of Cain's heart and not merely because of the physical offering Cain brought. This is supported by New Testament comments such as 1 John 3:12. Cain's angry response definitely reveals a darkened heart. Instead of being teachable, eager to adjust his offering or himself in order to be pleasing to God, Cain gets mad. His "face falls."
In the following verses, God will gently, lovingly warn Cain about the consequences of choosing anger over a willingness to change his path to please God. Cain's choice to ultimately choose anger and violence over submission speaks volumes of the state of his heart (Genesis 4:8).