When you sneeze, say:
الْحَمْدُ لِلَّهِ
Al-ḥamdu li-llāh
All praise is for Allah.
A companion should reply:
يَرْحَمُكَ اللَّهُ
Yarḥamuka llāh
May Allah have mercy on you.
The sneezer should then reply:
يَهْدِيكُمُ اللَّهُ وَيُصْلِحُ بَالَكُمْ
Yahdīkumu llāhu wa yuṣliḥu bālakum
May Allah guide you and set your affairs right.