If a person sneezes during his prayer, should he say ‘ Al-hamdu Lillaah (Praise be to Allaah)’? If he says it, should those who hear him say, ‘ Yarhamuk Allaah (may Allaah have mercy on you)’?
Praise be to Allaah.
Praise be to Allaah. Yes, he should say that, and anyone who hears him and is not himself praying should say ‘Yarhamuk Allaah’ to him.
From Fataawa al-Imaam al-Nawawi, p. 50.