Adam made love to his wife Eve. She became pregnant and gave birth to Cain. She said, "With the LORD's help I have had a baby boy."
References for Genesis 4:1
Later she gave birth to his brother Abel. Abel took care of sheep. Cain worked the ground.
After some time, Cain gathered some of the things he had grown. He brought them as an offering to the Lord.
But Abel brought the fattest parts of some of the lambs from his flock. They were the male animals that were born first to their mothers. The LORD was pleased with Abel and his offering.
But he wasn't pleased with Cain and his offering. So Cain became very angry. His face was sad.
Then the LORD said to Cain, "Why are you angry? Why are you looking so sad?