All great ones had their teachers. All the sages, saints, prophets, world teachers, incarnations, great men have had their own Gurus, however great they might have been. Svetaketu learnt the nature of Truth from Uddalaka, Maitreyi from Yajnavalkya, Bhrigu from Varuna, Narada from Sanatkumara, Nachiketas from Yama, Indra from Prajapati; and several others humbly went to wise ones, observed strict Brahmacharya, practised rigorous discipline, and learnt Brahma-Vidya from them.
Lord Krishna sat at the feet of His Guru Sandipani. Lord Rama had Guru Vasishtha who gave Him Upadesa. Lord Jesus sought John to be baptised by him on the banks of the river Jordan. Even Devas have Brihaspati as their Guru. Even the greatest among the divine beings sat at the feet of Guru Dakshinamurti.
-- Swami Sivananda