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Raghu was a ruler of the Ikshvaku dynasty. According to the Raghuvamsha, he was born to the king Dilīpa and his queen Sudakshina. His name in Sanskrit means the fast one, deriving from Raghu's chariot-driving abilities. So celebrated were the exploits of Raghu, that his dynasty itself came to be known as the Raghuvamsha or the Raghukula after him. The history of his dynasty is elaborated upon by Kalidasa in his Raghuvamsha.
After acceding to the throne, he expanded his kingdom in all four directions. Later, on the instruction of his Guru Vashistha, he performed Vishwajit Yajna and gave all his wealth as Dāna. After completion of Yajna when all the wealth was given as Dāna, Sage Kautsa, a disciple of Vartantu came, to whom Raghu asked, "what should be given to him as Guru-Dakshina?", to which Kautsa replied, "your Seva would suffice". Kautsa became furious when Raghu persisted repeatedly and said to him, "having learnt 14 Vidyas from me, you must give me 14 koti gold coins as Guru-Dakshina". Raghu, being a man of his words, asked him to rest in his palace and assured him of giving the Guru-Dakshina within a day.
Raghu commanded his army to gear up for invasion to Loka of Kubera on the following morning. When he was heading towards the Kuber Loka, his treasurer came to him and told him that Kubera, by the virtue of fear of Raghu, rained gold coins last night. Hence, Raghu gave those gold coins as Guru-Dakshina to Sage Kautsa and fulfilled his Vachan.
A number of Puranas, which include the Vishnu Purana, the Vayu Purana, the Linga Purana, mention Dirghabahu as the son of Dilīpa and Raghu as the son of Dirghabahu. But the Harivamsha, the Brahma Purana and the Shiva Purana mention Raghu as son of Dilīpa and Dirghavahu as his epithet.