?Will salaah be nullified by substituting a (QAAF) with a (KAAF)?

Q: Salaah-343: When reciting Surah Taariq, the Imaam substituted the (QAAF) in the phrase (LA QAWLUN FASL) with a (KAAF) The Imaam is capable of reciting properly, so will the salaah have to be repeated or not?

Answer: The salaah will have to be repeated in this case because when the ability to recite correctly exists, such an error will render the salaah null and void.

Fatawa Rahimiyyah vol.2