This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

He was a fugitive and a vagabond.

Genesis 4:11-12 View context

And now [art] thou cursed from the earth, which hath opened her mouth to receive thy brother's blood from thy hand;

When thou tillest the ground, it shall not henceforth yield unto thee her strength; a fugitive and a vagabond shalt thou be in the earth.

He settled down, married, had a son, and built a city.

Genesis 4:16-17 View context

And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden.

And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch.