https://torontodawah.com/a-person-should-only-say-may-allah-have-mercy-upon-you-when-he-is-certain-someone-has-said-all-praise-is-due-to-allah-after-sneezing-ibn-qayyim-al-jawziyya-and-shaykh-ibn-uthaymeen/
A Person Should Only Say: "May Allah Have Mercy Upon You" When He Is Certain Someone Has Said: "All Praise Is Due To Allah" After Sneezing - Ibn Qayyim Al-Jawziyya And Shaykh Ibn Uthaymeen