It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "The supplication that is accepted the quickest is the supplication made by a person for another in his absence."
Hadith Referenceالادب المفرد / كتاب / 623
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«ضعيف : أخرجه أبوداؤد ، كتاب الوتر ، باب الدعاء بظهر الغيب : 1535 و الترمذي : 1980 - انظر المشكاة : 2247»
Explanation & Benefits
Shaykh Maulana Usman Muneeb
Benefits and Issues: The chain of narration of this report is weak; however, the acceptance of a supplication made for a Muslim in his absence is established from authentic ahadith, as will be mentioned further ahead.
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 623