Genesis 4:1 Now Adam knew Eve his wife, and she conceived and bore Cain, saying, “I have gotten a man with the help of the LORD.” And again, she bore his brother Abel. Now Abel was a keeper of sheep, and Cain a worker of the ground. In the course of time Cain brought to the LORD an offering of the fruit of the ground, and Abel also brought of the firstborn of his flock and of their fat portions. And the LORD had regard for Abel and his offering, but for Cain and his offering he had no regard. So Cain was very angry, and his face fell. The LORD said to Cain, “Why are you angry, and why has your face fallen? If you do well, will you not be accepted? And if you do not do well, sin is crouching at the door. Its desire is contrary to you, but you must rule over it.”
Hebrews 11:4 By faith Abel offered to God a more acceptable sacrifice than Cain, through which he was commended as righteous, God commending him by accepting his gifts. And through his faith, though he died, he still speaks.
Numbers 18:12 All the best of the oil and all the best of the wine and of the grain, the firstfruits of what they give to the LORD
Isaiah 3:10-11 Tell the righteous that it shall be well with them, for they shall eat the fruit of their deeds. Woe to the wicked! It shall be ill with him, for what his hands have dealt out shall be done to him.
Jeremiah 2:5 Thus says the LORD: “What wrong did your fathers find in me that they went far from me, and went after worthlessness, and became worthless?
Ecclesiastes 8:12-13 Though a sinner does evil a hundred times and prolongs his life, yet I know that it will be well with those who fear God, because they fear before him. But it will not be well with the wicked, neither will he prolong his days like a shadow, because he does not fear before God.
The offerings of Cain and Abel were different. Cain showed a proud, unbelieving heart. Therefore he and his offering were rejected. Abel came as a sinner, and according to God’s appointment, by his sacrifice expressing humility, sincerity, and believing obedience. Thus, seeking the benefit of the new covenant of mercy, through the promised Seed, his sacrifice had a token that God accepted it. Abel offered in faith, and Cain did not, Heb 11:4. In all ages there have been two sorts of worshippers, such as Cain and Abel; namely, proud, hardened despisers of the gospel method of salvation, who attempt to please God in ways of their own devising; and humble believers, who draw near to him in the way he has revealed. Cain indulged malignant anger against Abel. He harboured an evil spirit of discontent and rebellion against God. God notices all our sinful passions and discontents. There is not an angry, envious, or fretful look, that escapes his observing eye. The Lord reasoned with this rebellious man; if he came in the right way, he should be accepted. Some understand this as an intimation of mercy. If thou doest not well, sin, that is, the sin-offering, lies at the door, and thou mayest take the benefit of it. The same word signifies sin, and a sacrifice for sin. Though thou hast not done well, yet do not despair; the remedy is at hand. Christ, the great sin-offering, is said to stand at the door, Re 3:20. And those well deserve to perish in their sins, that will not go to the door to ask for the benefit of this sin-offering. God’s acceptance of Abel’s offering did not change the birthright, and make it his; why then should Cain be so angry? Sinful heats and disquiets vanish before a strict and fair inquiry into the cause. (Henry)
Note in one word that we have here at the beginning of human history the solemn distinction which runs through it all. These two, so near in blood, so separate in spirit, head the two classes into which Scripture decisively parts men, especially men who have heard the gospel. It is unfashionable now to draw that broad line between the righteous and the wicked, believers and unbelievers. Sheep and goats are all one. Modern liberal sentiment-so-called-will not consent to such narrowness as the old-fashioned classification. There are none of us black, and none white; we are all different shades of grey. But facts do not quite bear out such amiable views. Perhaps it is not less charitable, and a great deal truer, to draw the line broad and plain, on one side of which is peace and safety, and on the other trouble and death, if only we make it plain that no man need stop one minute on the dark side. The foundation of a righteous character, determines the acceptableness of worship. Cain’s offering had no sense of dependence, no outgoing of love and trust, no adoration,-though it may have had fear,-and no moral element. So it had no sweet odour for God. Abel’s was sprinkled with some drops of the incense of lowly trust, and came from a heart which fain would be pure; therefore it was a joy to God. So we are taught at the very beginning, that, as is the man, so is his sacrifice; that the prayer of the wicked is an abomination. Plenty of worship nowadays is Cain worship. Many reputable professing Christians bring just such sacrifices. The prayers of such never reach higher than the church ceiling. Of course, the lesson of the story is not that a man must be pure before his sacrifice is accepted. Of course, the faintest cry of trust is heard, and a contrite heart, however sinful, is always welcome. But we are taught that our acts of worship must have our hearts in them, and that it is vain to pray and to love evil. Sin has the awful power of blocking our way to God. (MacLaren)