Matthew 7:6
"Do not offer sacred things to dogs, and do not throw your pearls in front of [wild] pigs [i.e., to those who will not appreciate them], because they will probably trample on them with their feet and then turn around and attack you.
Philippians 3:2
Watch out for the "dogs!" [Note: "Dogs" were viewed with disgust by the ancient Jews (Deut. 23:18; II Kings 8:13; Rev. 22:15), so the term is used here derogatorily for Jewish Christians who were trying to impose on the church the requirements of the law of Moses]. Watch out for the evil workers! Watch out for those who mutilate the body meaninglessly! [Note: Paul here alludes, in a derogatory wordplay, to the Jewish practice of circumcision].
2 Peter 2:22
It has happened to them like the true proverb [says], "The dog [throws up, and then] goes back and eats its own vomit," and "The hog that was all cleaned up [goes back] to wallowing in the mud."
Revelation 22:15
On the outside [of the city] are the dogs [Note: This probably refers to people who practiced sexual perversions. See Deut. 23:17] and the sorcerers, and the sexually immoral people, and the murderers, and the idolaters and every person who loves and practices falsehood.