Genesis 4:2-4

4:2 Then she gave birth to his brother Abel. Abel took care of the flocks, while Cain cultivated the ground.

4:3 At the designated time Cain brought some of the fruit of the ground for an offering to the Lord. 4:4 But Abel brought some of the firstborn of his flock – even the fattest of them. And the Lord was pleased with Abel and his offering,

Genesis 8:20

8:20 Noah built an altar to the Lord. He then took some of every kind of clean animal and clean bird and offered burnt offerings on the altar.