Such kind of conversation, as includes folly, and can no ways be profitable and interesting, Ephesians 5:4 . Facetiousness, indeed, is allowable, when it ministers to harmless divertisement, and delight to conversation; when it is used for the purpose of exposing things which are base and vile; when it has for its aim the reformation of others; when used by way of defense under unjust reproach. But all such kind of speaking as includes profane jesting, loose, wanton, scurrilous, injurious, unseasonable, vain-glorious talk, is strictly forbidden.
See Barrow's excellent Sermon on this subject in his Works, vol. 1: ser. 14.