Q: Salaah-72: I was reciting Surah Layl in the Isha salaah. when I recited (FASNUYASSIRHU LEEL YUSRAAH) instead of (FASNUYSIRHU LEEL ASRAA) Is the salaah valid?

Answer: In the stated case, salaah will be nullified if you joined the sentence (WA?KADDAB BIL HUSNI) with (FASNUYYSIRHU LEEL YUSRAH) However, if you stopped between the two sentences (took a breath in between), the salaah will not be nullified.6 And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2