It is narrated from Sayyiduna Khabbab (may Allah be pleased with him) that he said: We complained to the Messenger of Allah (peace and blessings be upon him) about the intensity of the heat, but he (peace and blessings be upon him) did not accept our complaint. I asked Abu Ishaq: About Zuhr? He said: Yes. I said: About praying it early? He said: Yes, about praying Zuhr early.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2065