‘When one of you sneezes he should say:
‘All praise if for Allah.’
…and his brother or companion should say to him:
‘May Allah have mercy upon you.’
…and he (i.e. the one who sneezed) replies back to him:
يَهْـديكُـمُ اللهُ وَيُصْـلِحُ بالَـكُم.
Yahdeekumul-lahu wayuslihu balakum.
‘May Allah guide you and rectify your condition.’