Musnad Ahmad 5:408

'Abdullah narrated to us, Abu Bakr ibn Abi Shaybah narrated to us, 'Ali ibn Mushir narrated to us, from Ibn Abi Layla, from 'Isa, from 'Abd al-Rahman ibn Abi Layla, from 'Ali, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "If one of you sneezes, let him say: 'Praise be to Allah, Lord of the worlds.' And let those around him say: 'May Allah have mercy on you.' And let him say: 'May Allah guide you and rectify your state.'"