Musnad Ahmad 788:92

'Affan narrated to us, he said: Hammam narrated to us, Abu 'Imran al-Jawni narrated to us, from Abu Bakr ibn 'Abd Allah ibn Qays al-Ash'ari, from his father, that the Prophet, peace and blessings of Allah be upon him, said: "The tent is a hollowed pearl, its length in the sky is sixty miles. In every corner of it, for the believer, are family members whom the others do not see." And perhaps 'Affan said: "For every corner."