The Prophet (SAW) said that we will be resurrected doing what we were doing at the moment of our death. We would be surrounded by mankind, waiting to be judged by our creator...saying swear words. "But I am just expressing myself.” It is a common excuse for people who swear often. According to a study done, people use about 80-90 swear words a day, on average. Swearing has become a part of every day language, especially in western culture. Now imagine getting our book of deeds on the Day of Judgment; our chance to see how many times we cussed in our entire life. For some it will be a few marks, but for others, pages upon pages.
Here are a few hadith that show the importance of guarding our speech:
Reported by Abu Sa`id Al-Khudri (RA), the Prophet (SAW) said,
"When the son of Adam gets up in the morning, all the limbs humble themselves before the tongue and say: `Fear Allah for our sake because we are with you: (i.e., we will be rewarded or punished as a result of what you do) if you are straight, we will be straight; and if you are crooked, we will become crooked.''' [At-Tirmidhi]
Sahl bin Sa`d (RA) reported: The Messenger of Allah (SAW) said,
"Whosoever gives me a guarantee to safeguard what is between his jaws and what is between his legs, I shall guarantee him Jannah.'' [Al-Bukhari]
Abu Hurairah (RA) reported: the Prophet (SAW) said,
"He who believes in Allah and the Last Day must either speak good or remain silent.'' [Muslim]
Allah knows best.