Do you know the actual reference off-hand?
Mark 9:43-48
FYI
1 Corinthians 5
Immorality Must Be Judged
9I wrote to you in my epistle not to keep company with sexually immoral people. 10Yet I certainly did not mean with the sexually immoral people of this world, or with the covetous, or extortioners, or idolaters, since then you would need to go out of the world. 11But now I have written to you not to keep company with anyone named a brother, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner--not even to eat with such a person.