“Thou shaft not steal” is at least as decisive against gambling as “Thou shalt not kill” against dueling.

The Catholic Answers

That is not true. No man has the right to alienate his life. Men have got the right to alienate their goods. And gambling is not stealing. If I take from Brown a dollar belonging to Brown against his will, I steal. But if we mutually agree to each putting a dollar in a hat and drawing lots as to which of us shall have the two dollars, we are not offending. We own our own money, and we can choose to renounce our possible possession of it in exchange for a lawful chance of winning the prize. I am willing that if he wins he shall have my dollar. He is willing that if I win I shall have his. There is no question of stealing from each other.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty