Mahabharata Anushasna Parva Chapter 150:3

Mahabharata Anushasna Parva (Dana Dharma Parva) Chapter 150:3 Atri, the illustrious Vasishtha, the great Rishi Kasyapa, Gotama, Bharadwaja, Viswamitra, the son of Kusika, and Richika's fierce son Jamadagni of great energy,—these seven are the Ritwiks of the Lord of treasures and dwell in the northern quarter. There are seven other Rishis that live in all directions without being confined to any particular one. They, it is, who are the inducers of fame and of all this beneficial to men, and they have been sung as the creators of the worlds. Dharma, Kama, Kala, Vasu, Vasuki, Ananta, and Kapila,—these seven are the upholders of the world. Rama, Vyasa, Drona's son Aswatthaman, are the other Rishis (that are regarded as the foremost). These are the great Rishis as distributed into seven groups, each group consisting of seven. They are the creators of that peace and good that men enjoy. They are said to be the Regents of the several points of the compass. One should turn one's face to that direction in which one of these Rishis live if one wishes to worship him. Those Rishis are the creators of all creatures and have been regarded as the cleansers of all. Samvarta, Merusavarna, the righteous Markandeya, and Sankhya and Yoga, and Narada and the great Rishi Durvasa,—these are endued with severe penance and great self-restraint, and are celebrated over the three worlds. There are others who are equal to Rudra himself. They live in the region of Brahman. By naming them with reverence a sonless man obtains a son, and a poor man obtains wealth. Indeed, by naming them, one acquires success in religion, and wealth and pleasure. One should also take the name of that celebrated king who was Emperor of all the earth and equal to a Prajapati, viz., that foremost of monarchs, Prithu, the son of Vena. The earth became his daughter (from love and affection). One should also name Pururavas of the Solar race and equal unto Mahendra himself in prowess. He was the son of Ila and celebrated over the three worlds. One should, indeed, take the name of that dear son of Vudha. One should also take the name of Bharata, that hero celebrated over the three worlds. He also who in the Krita age adored the gods in a grand Gomedha sacrifice, viz., Rantideva of great splendour, who was equal unto Mahadeva himself, should be named. Endued with penances, possessed of every auspicious mark, the source of every kind of benefit to the world, he was the conqueror of the universes. One should also take the name of the royal sage Sweta of illustrious fame. He had gratified the great Mahadeva and it was for his sake that Andhaka was slain. One should also take the name of the royal sage Bhagiratha of great fame, who, through the grace of Mahadeva, succeeded in bringing down the sacred river from heaven (for flowing over the earth and cleansing all human beings of their sins). It was Bhagiratha who caused the ashes of the sixty thousand sons of Sagara to be overflowed with the sacred waters of Ganga and thereby rescued them from their sin.