Musannaf Ibn Abi Shayba 27:277

Ubayd Allah ibn Musa narrated to us, from Sufyan, from Simak, from Habib ibn Hammaz, who said: It was said to Ali, "How did Dhu al-Qarnayn reach the East and the West?" He said, "The clouds were subjected to him, the light was spread out for him, and the means were extended for him." Then he said, "Shall I tell you more?" He said, "That is sufficient for me."