Musnad Ahmad Hadith 20595

Sa’sa’ah, who was the uncle of Farazdaq, says that he once presented himself before the Prophet (peace be upon him). The Prophet (peace be upon him) recited this verse before him: “Whoever does an atom’s weight of good will see it, and whoever does an atom’s weight of evil will see it.” He said, “This is enough for me. Even if I do not hear anything else besides this, I do not care.”