Sayyiduna Hakim bin Hizam (may Allah be pleased with him) narrates that once the Messenger of Allah (peace and blessings be upon him) was among his Companions when he (peace and blessings be upon him) said to them: "Do you hear what I hear?" The Companions said: We do not hear anything. He (peace and blessings be upon him) said: "I hear the creaking of the heaven, and it cannot be blamed for creaking. There is not a hand-span of space in the heaven but that an angel is upon it (worshipping Allah), either prostrating or standing."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3109