Adam and Eve had two sons named Cain and Abel.

Abel took care of the animals while Cain farmed the soil.

Cain offered food from the soil to God as an offering.
Abel brought the firstborn and best animals as an offering to the Lord.

God liked Abel's offering, but did not like Cain’s and this made Cain angry.

Then the LORD said to Cain, “Why are you angry? Why is your face so sad? If you do what is right, will you not be accepted? But if you do not do what is right, sin is waiting for you; it desires to have you, but you must rule over it.”

Later Cain decided to not do what was right. Cain asked Abel to go into the field where Cain killed his brother.

Then the LORD said to Cain, “Where is your brother Abel?”  Able lied to the Lord and said, “I don’t know, am I my brother’s keeper?”

Then God made Cain leave the farm and told him that from now on, “When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth.”

Then the LORD put a mark on Cain so that no one would kill him. So Cain left and lived the rest of his life in the land of Nod, east of Eden. Where his children built a city, made iron and bronze tools and created music.

Adapted from Genesis - Chapter 4