The Holy Scriptures condemn foul language, as St. Paul teaches in the Epistle to the Ephesians:

“Let no evil talk come out of your mouths, but only such as is good for edifying, as fits the occasion, that it may impart grace to those who hear. And do not grieve the Holy Spirit of God, in whom you were sealed for the day of redemption. Let all bitterness and wrath and anger and clamour and slander be put away from you, with all malice” (Eph 4:29-31).

Before this passage, the Apostle had already exhorted Christians to put off the old self, to renounce their past life and to be renewed inwardly, putting on the new self, created in the image of God (cf. Eph 4:22-24). Therefore, abandoning foul, coarse, and indecent language is part of the Christian’s conversion process, under pain of grieving the Paraclete.

In fact, indecent words often express angry, lustful, or vulgar thoughts, unworthy of a true disciple of Our Lord Jesus Christ, who must distinguish himself by a clear and elevated vocabulary, thus witnessing his charity and purity, for “out of the abundance of the heart his mouth speaks” (Lk 6:45). The terrible spread of bad language is a very significant symptom of the moral crisis afflicting the world. We notice more and more, in both public and private settings, the use of obscene and indecent expressions, which many even take pride in using.

In God, being and word are one and the same reality. The Word – affirms St. John – was with God and was God (cf. Jn 1:1). For men, however, it seems not to be so; the word sometimes differs from the being due to various circumstances, although this is not ideal. Created in the image and likeness of God (cf. Gn 1:26-27), we must seek harmony between what we are and what we express, so that something of our Creator may shine forth in us. Integrity, as the Catechism of the Catholic Church explains, “tolerates neither a double life nor duplicity in speech” (CCC 2338).

There is yet another reason to consider the seriousness of resorting to vulgarities in order to habitually express oneself, in moments of anger or agitation. So-called “swear words” are usually indecent, as they refer to realities related to the scope of the Sixth Commandment of the Law of God.

St. Paul also teaches in the Letter to the Ephesians: “Let there be no filthiness, nor silly talk, nor levity, which are not fitting” (Eph 5:4). The vulgarity and lust present in impure words stain and disfigure the soul of the one who pronounces them and, in a certain way, also wound the dignity of the one who hears them. Oral expression reflects the interior of the heart, and at the same time moulds and influences it. Therefore, indecent language represents an attack on “God’s temple” (1 Cor 3:16) which is the human being. And this is why St. Paul censures it so severely.

Finally, it is worth emphasizing that having respectful, dignified, and elevated language is an indispensable part of good Christian comportment, courtesy, and apostolate.