Needless to say that gheebat is a most serious major sin...
Needless to say that gheebat is a most serious major sin which will not be forgiven by Allah Subhanahu wa Ta'ala unless the victim of the gheebat forgives that person. Late Ayatullah Khomayni has written in reply to a question that praying furada in a place where congregational prayer is being conducted is not Ja'ez (lawful), although the prayer is valid." (See Istifata'at, Vol.1, p. 164).
b) If an individual (reasons best known to himselj) doesn't want to pray in congregational prayers due to any particular Imam (leader), is he permitted to pray everyday a furada namaaz (separately) during the same time and at the same mosque when congregational prayers are being conducted?
A: Late Ayatullah al-Khoui was asked by two persons separately about this problem; one of them wrote: "Zayd (who is respected by people) enters a mosque when a congregational prayer is going to be held behind an Imam whom Zayd thinks is not qualified for it, because he is not 'Adil' or his makhraj is not correct or because of some other reason.
People rely on Zayd's opinion and respect it; if he prays behind him because of taqiyah or just pretends to join the congregation (while having niyyat of Furada), the mu'mineen will surely take it as a confirmation of that Imam's qualifications and think that it is lawful to pray behind him. Now what should Zayd do? Should he pray behind that Imam? Or should he go out (of the mosque)?
Or should he pray furada (separately) which would be an insult to the Imam?" Late Ayatullah al-Khoui replied: "In the situation mentioned in the question, his only option is to go out. And Allah is Knowing." (See Masa'il wa Rudud, Qum, Vol.1, pages 33-34). Another person asked about the same problem with a slight difference: He was in a gathering and when time of prayer came, congregational prayer was arranged behind someone who, in his views, was not fit for it.
If he goes out, it will reflect badly on the said Imam, and if he joins the prayer with niyyat of furada, others will take.it as a confirmation of the qualifications of that Imam. Late Ayatullah al-Khoui replied: "In this situation he may get out by pretending that his nose had started beleeding, or that he had got sovere stomach-pain or something like that." (See Munyatus-sa'il. 3rd cd., 1412, Qum. p. 39).
c) Is it permissible for an individual (praying furada) to recite the two suras loudly at the same time and place where congregational prayers are being conducted and performed?