Sarah, the daughter of Sayyiduna Ibn Mas'ud (may Allah be pleased with him), narrates that her father told her that he was walking behind the Messenger of Allah (peace and blessings be upon him) when one of his Companions, or some of them, pushed him. So the Messenger of Allah (peace and blessings be upon him) said: "By the One in whose hand my soul is, Abdullah will be heavier in the Scales on the Day of Resurrection than Mount Uhud," as though they had been amazed at his (physical) lightness.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8422