If a person starts to recite a surah that contains an obligatory sajdah – whether he does so intentionally or inadvertently – in the event that he realises this before reciting the verse that contains the obligatory sajdah, he can stop reciting that surah and recite another surah instead. If he realises after reciting the verse that contains the obligatory sajdah, he must act according to the instructions mentioned in the previous ruling.