You probably know the story of the first murder.
Cain and his brother Abel brought their sacrifices to God. Cain was a farmer and brought to God an offering of his labors; Abel was a shepherd, and he brought an offering of his labor. Then the Bible states that the Lord respected Abel and his offering, but He did not respect Cain and his offering. And Cain was very angry (Genesis 4:4, 5). It wasn’t merely Cain’s offering which God rejected, it was Cain himself! So Cain slew his brother Abel.
Why did God reject Cain and his offering? Some people assume it’s because God didn’t want offerings of grain or fruits. In fact, under the later Law of Moses, offerings of grain and grape were desired by God (Leviticus 2:14-15; 23:13).
Using Scripture to speak concerning itself, Hebrews 11:4 explains why God accepted Abel but not his brother Cain. By faith Abel offered to God a more excellent sacrifice than Cain, through which he obtained witness that he was righteous, God testifying of his gifts, and through it he being dead still speaks.
Abel came to God in faith, while Cain came out of habit, religion, tradition, duty or self-righteousness. These all are what we might term works of righteousness which we have done (Titus 3:5).
Though Abel has been dead for thousands of years, he still preaches to us today. His message is that there is only one way to acceptance with God and it’s through faith.
Without faith it is impossible to please Him (Hebrews 11:6). For by grace you have been saved through faith, and that not of yourselves, it is the gift of God, not of works, lest anyone should boast (Ephesians 2:8-9).