Musnad Ahmad 788:199

Yazid ibn Harun narrated to us, he said: Hammam ibn Yahya informed us, from Abu Imran al-Jawni, from Abu Bakr ibn Abi Musa, from his father, from the Prophet, may God bless him and grant him peace, who said: "The tent is a hollow pearl, its height in the sky is sixty miles. In every corner of it, there are family members for the believer, and the others do not see them."