Sahih Muslim Book 8, Hadith Number 3440.
Chapter: Tracing of relationship from physical features.
‘Aisha (Allah be pleased with her) reported: One day Allah’s Apostle (May peace be upon him) visited me looking pleased and he said: ‘Aisha, don’t you see Mujazziz al-Mudliji? (He) entered (my house) and saw Usama and Zaid with a rug over them covering their heads, but their feet appeared, and (he) said: These feet are related to one another.