Matt. 5:34 But I say to you, make no oath at all, either by heaven, for it is the throne of God, 35 or by the earth, for it is the footstool of His feet, or by Jerusalem, for it is the city of the great King. 36 Nor shall you make an oath by your head, for you cannot make one hair white or black. 37 But let your statement be, ‘Yes, yes’ or ‘No, no’; anything beyond these is of evil.
James 5:12 But above all, my brethren, do not swear, either by heaven or by earth or with any other oath; but your yes is to be yes, and your no, no, so that you may not fall under judgment.
Ephesians 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 1:26 If anyone thinks himself to be religious, and yet does not bridle his tongue but deceives his own heart, this man's religion is worthless.
Luke 6:45 The good man out of the good treasure of his heart brings forth what is good; and the evil man out of the evil treasure brings forth what is evil; for his mouth speaks from that which fills his heart.
Eph. 5:4 and there must be no filthiness and silly talk, or coarse jesting, which are not fitting, but rather giving of thanks.
...and many more.
You think profanity and swearing are sin?
I say "yes" especially if they cause a brother or another to stumble.
And if we are accountable for every idle word, how are going to explain cussing and fussing to Holy God?