It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): the Prophet (peace and blessings be upon him) said: "Show mercy to whoever is on the earth, and the One who is in the heaven will show mercy to you."
Abu Ya'la, and al-Tabarani in all three of his books, recorded it. The narrators of Abu Ya'la are the narrators of the Sahih, except that the narrator Abu Ubaydah did not hear from his father, so this narration is mursal.
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