Ibn Masud was gathering siwak twigs from an arak tree. He had very thin legs, and the wind kept knocking him off balance. The people laughed at him.The Messenger of Allah ﷺ asked, "What are you laughing at?"They replied, "Prophet of Allah, at how thin his legs are."He said, "By the One in whose hand my soul is, those two legs will weigh heavier on the scale than Mount Uhud."
أنه كان يجتني سواكا من الأراك، وكان دقيق الساقين، فجعلت الريح تكفؤه، فضحك القوم منه، فقال رسول الله ﷺ: مم تضحكون؟ قالوا: يا نبي الله من دقة ساقيه، فقال: والذي نفسي بيده لهما أثقل في الميزان من أحد.
Ahmad (3991), Abu Yaala (5310), Bazzar - Kashf Astar - (2678), and Tabarani in Al-Kabir (8452) all narrated it, all of them through the route of Asim, from Zirr bin Hubaysh, from Ibn Masud, and he related it. Ibn Hibban (7069) graded it sahih and narrated it through this same route. Its chain of transmission is hasan because of Asim, who is Ibn Abu Najud, concerning whom there is disagreement, though his hadith is hasan.Ibn Kathir said in Al-Bidayah wal-Nihayah (19/506), "Ahmad alone narrated it (that is, among the authors of the six books), and its chain of transmission is strong and sound."Taken together, these hadiths indicate that what is weighed on the scale on the Day of Resurrection is the deed, the doer, and the record of his deeds.