All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
"Rafath" is forbidden for a fasting person as Abu Hurayrah narrated that the Prophet said: “Allah, the Almighty and Master of Honor says: “All the deeds of the sons of Adam are for them, except fasting, it is for Me [it is done for my sake], and I will give the reward for it.' Fasting is a shield or protection from the fire and from committing sins. If one of you is fasting, he should avoid sexual relation with his wife and quarreling, and if somebody fights or quarrels with him, he should say, 'I am fasting.' (I swear) By Him in Whose Hands my soul is, the unpleasant smell coming out from the mouth of a fasting person is better in the sight of Allah than the smell of musk. There are two pleasures for the fasting person, one at the time of breaking his fast, and the other at the time when he will meet his Lord; then he will be pleased because of his fasting.” [Al-Bukhari and Muslim]
Rafath here means uttering bad words. Al Qurtubi said: “This Hadeeth does not imply that the non-fasting person is allowed to do such a thing (Rafath) What is meant is that fasting makes this prohibition more emphatic.”
Allah knows best.