Sayyiduna al-Rabi' bin Anas (may Allah be pleased with him) narrates: The lowest heaven is a 'makfuf' (restrained) tablet, the second heaven is rock, the third is iron, the fourth is brass, the fifth is silver, the sixth is gold, and the seventh is ruby.
Al-Tabarani recorded it in al-Mu'jam al-Awsat in this way, as a mawquf report (stopping) at Sayyiduna al-Rabi' bin Anas (may Allah be pleased with him), and perhaps (the rest) has dropped out of the manuscript. Its chain contains a narrator, Abu Ja'far al-Razi, whom Abu Hatim and others declared thiqah (trustworthy), while al-Nasa'i (may Allah have mercy on him) and others called him da'if (weak). The remaining narrators of this report are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13365