It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), he said: When any one of you sneezes, he should say «الحمد للہ رب العالمین», and the one who responds should say «يرحمك الله», then the one who sneezed should say: «يغفر الله لي ولكم» May Allah forgive me and you as well.
Hadith Referenceالادب المفرد / كتاب العطاس والتثاؤب / 934
Hadith Gradingالألبانی:صحيح الإسناد موقوفًا
Hadith Takhrij«صحيح الإسناد موقوفًا : المعجم الكبير للطبراني : 162/10»
Explanation & Benefits
Shaykh Maulana Usman Muneeb
Benefits and Issues: From these narrations, it is understood that there is allowance for adding "Rabb al-'Alamin" to "Alhamdulillah" and for saying "Yaghfir lana wa lakum" in place of "Yahdikum Allah." However, the most virtuous and preferred practice is to suffice with those words that are authentically established as marfu' (attributed directly to the Prophet sallallahu alayhi wa sallam).
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 934