Genesis 4:2 – 4
New International Version (NIV)
2 Later she gave birth to his brother Abel.
Now Abel kept flocks, and Cain worked the soil. 3 In the course of time Cain brought some of the fruits of the soil as an offering to the Lord. 4 And Abel also brought an offering — fat portions from some of the firstborn of his flock. The Lord looked with favor on Abel and his offering,
From BibleGateway.com: http://www.biblegateway.com/passage/?search=Genesis+4.2-4&version=NIV