Cain initially was a religious man, evidently proud of his achievements as a "tiller of the ground" which God had "cursed" (Genesis 4:2; 3:17). He assumed that God would be much impressed with the beautiful basket of his "fruit of the ground" which he presented as an "offering unto the LORD." Cain became bitterly angry when God "had not respect" to Cain and his offering (Genesis 4:3-5).
"By faith Abel offered unto God a more excellent sacrifice than Cain," shedding the blood of an innocent lamb in substitution for his own sin and guilt before God, "by which he obtained witness that he was righteous" (Hebrews 11:4). Since "faith cometh by hearing, and hearing by the word of God" (Romans 10:17), Abel was merely obeying God's Word, but Cain, proud and self-righteous in attitude, was presuming to offer up his own merits in payment for the privilege of coming to God.
This was a "false gift," however, with no meritorious value at all before God, "like clouds and wind without rain." The apostle Jude warns against any such presumption, especially now that we can freely come to God through His own perfect "Lamb of God, which taketh away the sin of the world" (John 1:29). "Woe unto them!" says Jude, "for they have gone in the way of Cain . . . clouds they are without water, carried about of winds; trees whose fruit withereth, without fruit, twice dead, plucked up by the roots" (Jude 11-12). This severe indictment was lodged against all who, like Cain, are superficially religious, but who, by their self-righteous resentment against God, are "turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ" (Jude 4). We must not boast of our gifts to God, but only of His gift to us. HMM