Should a Christian refrain from swearing?
The Bible says clearly that unwholesome speech is a sin:
Eph. 4:29 Let no unwholesome word proceed from your mouth, but only such a word as is good for edification according to the need of the moment, so that it will give grace to those who hear.
James 3:8 But no one can tame the tongue; it is a restless evil and full of deadly poison.
James 3:9 With it we bless our Lord and Father, and with it we curse men, who have been made in the likeness of God;
James 3:10 from the same mouth come both blessing and cursing. My brethren, these things ought not to be this way.
James 3:11 Does a fountain send out from the same opening both fresh and bitter water?
James 3:12 Can a fig tree, my brethren, produce olives, or a vine produce figs? Nor can salt water produce fresh.
Therefore, cursing (using profanity) is sinful behavior that every Christian should avoid.