Cain brought an offering of fruit from his labors and Able brought an offering to the Lord of a lamb from his flock. God regarded Abel's offering, and Cain became jealous.
5 but for Cain and his offering he had no regard. So Cain was very angry, and his face fell.
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.
Hebrews 9
22 Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.
Proverbs 3
9 Honor the LORD with your wealth and with the firstfruits of all your produce;