Al-jawab billahi at-taufeeq (the answer with Allah’s guidance)
1) It is haraam to use such language, Allah mentions this language as Al-Laghw (dirty, false, evil vain talk, falsehood, and all that Allâh has forbidden) in the Quran.
“And those who turn away from Al-Laghw (dirty, false, evil vain talk, falsehood, and all that Allâh has forbidden). ” (Surah Number: 23, Ayah Number: 3)
The definition of Laghw is very broad. It includes Lies, sin, Shirk, evil speech, anything without benefit etc.
Thus Ulama have mentioned that there are different categories of Laghw, each with a different ruling.
The Highest type of Laghw (and thus the worst type) is that speech which is sin and disobedience i.e. in addition to it having no deeni benefit, it contains deeni harms. It will be necessary and Fard to stay away from this type of Laghw. -This includes foul language etc.
The lowest stage would be such speech that carries no benefit nor any harm. It would be better to stay away from this type.
Many Ayaat of the Quraan and many Ahadith show that a person cannot be a perfect believer until he abstains from this type of Laghw.
(Ma’ariful Quran Vol. 6 Pg. 296, Ahkaamul Quraan of Jassaas Vol.2 Pg.43)
By using such foul language one intends to hurt one another. Allah Ta’ala says,
“And those who annoy believing men and women undeservedly, bear on themselves the crime of slander and plain sin. ” (Surah Number: 33, Ayah Number: 58)
Ibn Mas’ud narrates that Prophet (sallallahu alaihi wa sallam) said, “To swear at a Muslim is sinful and to kill a muslim is kufr (disbelief). (agreed by Bukhari & Muslim)
So, One should control their tongues to avoid such languages. Nabi (sallallaahu alayhi wassallam) is reported to have stated that, “Paradise is for the man who controls his tongue.” Another Hadith states that, “The faith of a servant (of Allah Ta’ala) cannot be straight until his heart is straight, and his heart cannot be straight until his tongue is straight.”
2) If you swear whilst having wudhu, the wudhu will still remain intact. However, it is best to renew the wudhu.
and Only Allah Ta’ala Knows Best .
Moulana Qamruz Zaman