Sahih Adab al-Mufrad

Sayyiduna Ali (may Allah send blessings upon him) says, the Prophet (peace and blessings of Allah be upon him) ordered Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him) to climb a tree and bring a miswak or something similar from it. So his companions saw Sayyiduna Abdullah bin Mas’ud’s (may Allah be pleased with him) shin, and when they saw his thin shins, they laughed. Upon this, the Messenger of Allah (peace and blessings of Allah be upon him) said: “What are you laughing at? Abdullah’s leg will be heavier on the scale (on the Day of Resurrection) than Uhud (mountain).”