Duaa for One’s brother in his Absence

عن أبي الدرداء رضي الله عنه : أن رسول الله صلى الله عليه وسلم  كان يقول : دعوة المرء المسلم لأخيه بظهر الغيب مستجابة ، عند رأسه ملك موكل كلما دعا لأخيه بخير قال الملك الموكل به: آمين ، ولك بمثل. (مسلم رقم 2733)

Hadhrat Abu Dardaa (Radhiyallahu Anhu) reports that Rasulullah (Sallallahu Alaihi Wasallam) used to say: “The duaa made by a Muslim for his brother in his absence is accepted. Whenever he makes duaa for goodness for his brother, there is an angel that is appointed to stand at his head-side. The appointed angel says Ameen to his duaa and the angel makes duaa for him saying: ‘May Allah grant you the likeness of what you have asked for your brother.’”