Ephesians 5:3-5 comes out and says it

But sexual immorality and all impurity 

or covetousness must not even be named among you, 

as is proper among saints. 

Let there be no filthiness nor foolish talk nor crude joking, which are out of place, but instead let there be thanksgiving. 

---For you may be sure of this, 

that everyone who is sexually immoral or impure, 

or who is covetous (that is, an idolater), 

---has no inheritance in the kingdom of Christ and God.
Ephesians 5:3-5 ESV