1 Peter 3:15
But instead, set aside a place in your hearts where Christ is [in full control as] Lord, and be prepared always to give a suitable reply to every person who asks you for a reason why you have an inner hope. But [be sure you do it] in a meek and respectful way, however.
Matthew 12:34
You children of snakes! Since you are evil, how do you expect to speak good things? For the mouth speaks what the heart is filled with.
Titus 1:10-11
For there are many rebellious people, especially among the circumcision [i.e., the Jews], whose talk is useless and who deceive people.
James 3:6-8
And the tongue is [like] a fire [i.e., like that spark]. [For] the tongue, as a part of the body, is [like] the world of evil. It corrupts the entire life [of a person] and inflames the course of nature itself [i.e., it affects a person throughout his whole earthly existence], and is ignited by hell itself [i.e., the evil produced by the fiery tongue has hell as its source and destiny].
2 Peter 2:18
[Although] their talk is big, what they say is worthless, and by [offering people] fleshly desires [i.e., sexual gratification], they lead people astray, who are barely escaping from the error of the world.