It is narrated from al-Rabi' bin Anas (may Allah have mercy on him) that he said: "The reality of the heavens is that the first of them is a restrained wave (a held-back surge of water), the second is made of rock, the third of iron, the fourth of copper, the fifth of silver, the sixth of gold, and the seventh heaven of ruby."
This report is narrated from al-Rabi' bin Anas (may Allah have mercy on him) as mawquf. Although the narrator in its chain, Abu Ja'far al-Razi, has been called da'if (weak) because of criticism of his memory, his narration from al-Rabi' bin Anas is considered reliable.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب بدء الخلق / 3431
Hadith Gradingمحدثین:إسناده ضعيف، مقطوع
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :هذا أثرٌ مقطوع، إسناده ضعيف، لضعف أبي جعفر الرازي » «أخرجه المعجم الأوسط للطبراني برقم: 5661»