Sayyiduna Imran bin Husayn (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "A man's supplication for his brother made in his absence is not rejected."
Imam al-Bazzar recorded this narration.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدعية / 17234