Thomas Boston writes concerning the seventh commandment (not an endorsement of Thomas Boston as a true Christian). Specifically, unclean and filthy communication (cf. Ephesians 4:29):
“They are the discoveries of a filthy heart; for ‘out of the abundance of the heart the mouth speaketh,’ contrary to nature, propaling [sic] those things which nature teaches to keep secret. They are snares to the hearers; and to speak of them for delight is to act the filthiness in words, when they cannot do it otherwise. Neither will the art some have in dressing up their filthy notions in figurative terms excuse; but these in some sort are most dangerous, because the devilish wit displayed in them makes them more sticking; and so by means of the like phrases occurring in holy exercises, they are the readier even to defile these. Of this sort are filthy songs and ballad singing; and the delightful listening to such things, as the simple youth did to the speeches of the adulterous whore, Prov. vii. 18, 21″ (Thomas Boston, Commentary on Westminster Shorter Catechism).
“Come, let us take our fill of love until the morning: let us solace ourselves with loves. For the goodman [is] not at home, he is gone a long journey: He hath taken a bag of money with him, [and] will come home at the day appointed. With her much fair speech she caused him to yield, with the flattering of her lips she forced him. He goeth after her straightway, as an ox goeth to the slaughter, or as a fool to the correction of the stocks; Till a dart strike through his liver; as a bird hasteth to the snare, and knoweth not that it [is] for his life” (Proverbs 7:18-23)
“And it shall come to pass in that day, that Tyre shall be forgotten seventy years, according to the days of one king: after the end of seventy years shall Tyre sing as an harlot. Take an harp, go about the city, thou harlot that hast been forgotten; make sweet melody, sing many songs, that thou mayest be remembered. And it shall come to pass after the end of seventy years, that the LORD will visit Tyre, and she shall turn to her hire, and shall commit fornication with all the kingdoms of the world upon the face of the earth” (Isaiah 23:15-17).
Thomas Boston continues on the aforementioned commandment and types of behavior it forbids:
“Impudent and light behaviour, and immodest gestures, Isa. iii. 16.; indecent postures, contrary to religion and good manners. These are hellish matters of sport, that defile the actors, and those that are witnesses to them without abhorrence. And on this ground stage-plays and filthy pictures are amongst the things forbidden in this command, Ezek. xxiii. 14, 16” (Thomas Boston, Commentary on Westminster Shorter Catechism).
“And [that] she increased her whoredoms: for when she saw men pourtrayed upon the wall, the images of the Chaldeans pourtrayed with vermilion, Girded with girdles upon their loins, exceeding in dyed attire upon their heads, all of them princes to look to, after the manner of the Babylonians of Chaldea, the land of their nativity: And as soon as she saw them with her eyes, she doted upon them, and sent messengers unto them into Chaldea” (Ezekiel 23:14-16).
“I will set no wicked thing before mine eyes: I hate the work of them that turn aside; [it] shall not cleave to me. A froward heart shall depart from me: I will not know a wicked [person]” (Psalm 101:3-4).