Though there is no explicit explanation given in the Genesis narrative as to why God rejected Cain’s offering, it seems to me that the cumulative evidence in this case argues that Cain’s transgression consisted of more than just offering an inferior gift.
Here are my reasons.
Abel’s Gift Was More Excellent
While the adjective
pleion (rendered “more excellent”) basically means greater either in quantity or quality, it can also denote that which is superior by reason of inward worth.
For example, in the Sermon on the Mount, Jesus said that life is more than food. Life’s intrinsic greater value is in view.
There may be, therefore, a suggestion here that involves the nature of the gift offered (see below).
As in any case, however, the context of Hebrews 11:4 will have to determine the meaning of the word in that setting.
Abel’s Gift Was By Faith
When the expression “by faith” is employed in Hebrews 11:4ff with reference to the great characters of the Old Testament, it connotes the concept of obedience time and time again.
Verse eight explicitly says what the other passages imply, “By faith Abraham . . . obeyed.”
This principle becomes even more vivid when one compares the various examples of Hebrews 11 with their Old Testament background.
For instance, “By faith Noah . . . prepared an ark” (Heb. 11:7). As Moses shows in the Genesis narrative, this means he was strictly obedient to the divine instructions (Gen. 6:22).
To offer sacrifices by faith was to offer in harmony with sacred revelation (cf. Rom. 10:17), rather than the exercise of human “will-worship” (Col. 2:23).
The fact that these two brothers apparently brought their offerings at the same time may suggest that a heavenly instruction had been given. In view of the surrounding context, therefore, it appears that Cain’s sin was one of outright disobedience, not merely a weakness in giving that which was inferior.
Abel’s Gift Was Pleasing to God
The narrative in Genesis 4 leaves the impression that the type of offering made was the determining factor that brought God’s favor upon Abel, but not upon Cain.
Consider this. If the offering made was on account of sin (and the text does not explicitly say), then it would be reasonable to assume that a blood offering had been required (cf. Heb. 9:22). This could account for the Lord’s displeasure.
The comments of Professor Ralph Earle, in my judgment, are helpful here. He notes one idea regarding this matter:
Cain brought a bloodless offering, and thus offended Deity by posing as righteous and not in need of any sacrifice for sin. This theory has strong theological appeal. It assumes previous divine instruction as to what type of offering must be brought for making atonement for sin. There is indication that such a revelation had been given by the use of the verb form in Gen. 4:3 that can mean customary action (2003, 284).
Perhaps this is what the Hebrews writer alludes to in that God bore witness with respect to his gifts that Abel was “righteous.”
And so, while it may be the case that Abel’s offering was of better quality than his brother’s, it seems likely that there was a greater intensity of disobedience on Cain’s part than mere selfishness in offering a less valuable gift.
When Jude places Cain in a catalog of vile rebels, he seems to confirm our view of the character of Adam’s first child (Jude 11).
See also: Why Was Cain’s Sacrifice Rejected?