John Gill's Exposition of the Whole Bible
Proverbs 20:19
He that goeth about [as] a talebearer revealeth secrets,.... Or, "he that revealeth secrets goeth about as a talebearer"; a man that has really got the secrets of others out of them respecting themselves and families, and the affairs of them, or however pretends he master of them; goes about telling his tales from house to house, to the great prejudice of those whose secrets he is entrusted with, or pretends to be; and to the great prejudice of those to whom he tells them, as well as to his own; this is contrary to the law of Moses, and the rules of Christianity, Leviticus 19:16;
therefore meddle not with him that flattereth with his lips; or "mingle not with him" g; do not associate with him, do not keep him company, have nothing to say to him or do with him; for when he flatters you, and highly praises and extols you, he has a design upon you to get what he can out of you, in order to expose you elsewhere; therefore suspect him, be upon your guard, shun him and avoid him. It may be applied to false teachers, and their deceptions with good words and fair speeches; the word used signifies to deceive with the lips; see Romans 16:18; and well agrees with the parasites of Rome, Revelation 18:23.
g לא תתערב "non miscebis te", Pagninus, Montanus; "ne misceas te", Baynus, Mercerus; "ne admisceto te", Junius Tremellius, Piscator "ne commiscearis", Michaelis; "ne admisceas te", Schultens.