«من دعا لأخيه بظهر الغيب قال الملك الموكل به: آمين ولك بمثله»
The Prophet (peace and blessings be upon him) said:
"Whoever supplicates for his brother in his absence, the angel appointed over him says: 'Amin, and for you the like of it (be granted).'"
Hadith Referenceصحیح الجامع الصغیر / حرف الميم / 6235