Ephesians 4:23, 29

and be continually renewed in the spirit of your mind [having a fresh, untarnished mental and spiritual attitude]

Do not let unwholesome [foul, profane, worthless, vulgar] words ever come out of your mouth, but only such speech as is good for building up others, according to the need and the occasion, so that it will be a blessing to those who hear [you speak].