Janab Mufti saheb, Ashlamu alaiykum, Mera sawal yeh hai ke kya koi non-muslim ka humne koi achcha kam kiya ho aur woh non-muslim yeh kahe ke may god bless you ya apne dil me hi duva kare to kya is duva ka badala hume milta hai, mere matlab hai ki kya allah kafir ki duva kabul karta hai. Dusara ye ke jab koi non-muslim ne humara liye (for muslim) achcha kam kiya ho to kya hum use yeh kam sakte hai ki allah tumhari ummar daraj kare, ya allah tumhe rozi de ya allah tume salamt rakhe, aisi duva ek non-muslim ke liya ek muslim kar sakta hai ya nahi. sukriya
Answer
(Fatwa: 1/19=H/1429)
You shall certainly get the reward of sympathy, good conduct and help rendered to him. If he was impressed by your behaviour and prayed for you then also you shall get the benefit, in-sha-Allah. The prayers of non-Muslims in the world are also accepted.
(2) In this case, one should say: hadakAllah or jazakAllah; these are comprehensive duas to any non-Muslim.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband