The Ribhus (Sanskrit: ऋभु, ṛbhu) are three at first mortal beings who according to Sayana attained godhood by austerities. Their individual names were Ribhu (or Rhibhu), Vaja and Vibhvan, but after the name of their leader they were collectively called Rhibhus or Ribhus (ṛbhú-, pl. ṛbhava). Their name's meaning is "clever, skillful, inventive, prudent", cognate to Latin labor and Gothic arb-aiþs "labour, toil", and perhaps to English elf. In the Rigveda the adjective in its lexical meaning "skillful" is also applied to Indra, Agni and the Adityas.
Origin and meaning 
The Ribhus were first mentioned in the oldest Hindhu scriptures of the Rigveda, wherein eleven hymns are dedicated to them (RV 1.20, 110, 111, 161, RV 3.60, RV 4.33-37, RV 7.48), and the Atharvaveda. They are said to be the sons of Sudhanvan, a descendant of Angiras. In later Hindu mythology (Vishnu Purana Book 2, Chapters 15 - 16 and the Song of Ribhu) Ribhu (or Rhibhu), supposed to be the leader of them, is said to be a son of Brahma. Unlike that identification the "Puranic Encyclopedia" states that this Ribhu is not identical with the leader of the Rhibhus whose name therein is Rbuksan. They are supposed to dwell in the solar sphere; Aitareya Brahmana III, 30 describes them as "sun's neighbours or pupils". On Earth they appeared generally as accompanying Indra, especially at the evening sacrifice and as Gods they were besought to grant boons to their worshipers, especially dexterity.
The Ribhus are artists who formed the horses of Indra, the carriage of the Ashvins, and the miraculous cow of Brihaspati, made their parents young, and performed other wonderful works which according to RV 4.51.6 were "done by the dawn". According to Yaska they also founded the sacrifices. They are supposed to take their ease and remain every year for twelve days idle in the house of Agohya (an appellation of Aditya which means "one who cannot be concealed", therefore the Sun). When the Devas (gods) heard of their skill, they sent Agni to them, bidding them, to construct four cups from the one cup of Tvashtar, the artificer of the devas. When the Ribhus successfully had executed this task, the devas received them among themselves, gave them immortality and allowed them to partake of their sacrifices.
Three Seasons 
According to Yaska and Sayana the Ribhus represent the rays of the sun. David Frawley states about that notion, that "Vedic gods, like the Adityas, Maruts, Vasus and Rhibhus, often appear as rays of the sun, as stars or constellations" Bal Gangadhar Tilak, stating that the interpretation of Yaska and Sayana could not explain their number, interpreted them 1893 referring to "several European scholars" as representing the three seasons of the year of the early Vedic period. The Satapata Brahmana XIV.I.1.28 mentions "three divisions of the year" and in RV 1.164.48 the "three spokes" are supposed to mean this three seasons. But Tilak didn't show a relation of their name and works to this interpretation. So A. Berriedale Keith 1925 mentioned that "the assertion that the Rbhus are really the Rthus" (the seasons) "is not 'in the slightest degree plausible'".
Twelve intercalary Days 
According to Bal Gangadhar Tilak referring to RV 1.161.13 the twelve days, when the Ribhus rested at the house of Agohya, took place "at the end of the year". He describes them as the holiest days of the year of which the ancestors of today's Indians believed, that the devas then would leave heaven to visit the homes of the humans. As David Frawley mentioned in context of the seasons, according to RV 7.103.7 - 8 also the as long Atiratra rite of Soma was celebrated at this time.
Bal Gangadhar Tilak further interpreted the hound or dog, which according to RV 1.161.13 woke the Ribhus, as the "dogstar" Sirius, which appears at the vernal equinox "at the end of the Pitriyana". The "Pitriyana" (meaning "the path of the fathers", called Pitrs), are the six southern signs of the Zodiak, by Tilak also called "the eternal waters of Yamaloka". Illustrative Maitrayani Upanishad VI, 1 describes the year as divided into two halfes, one of which belongs to Agni (Fire) and the other to Varuna (Water). Thus according to Bal Gangadhar Tilak in 1893 the year started at the time of the Rigveda at the vernal equinox and the Ribhus recommenced working after their awakening in the beginning of the new year. William Dwight Whitney 1895 rejected this interpretation by Tilak. In this context Tilak also pointed to the fact that because of RV 1.161.13 not the solar year but the anticlockwise movement of the precession of the equinoxes must be meant which he calls an "equinoctial year", but he didn't refer to this in his further interpretation.
Bal Gangadhar Tilak then interpreted also in 1893 the Period of twelve days as the twelve intercalary days, to fix the difference between the lunar year of 354 days and the solar year of 366 days. While he interpreted the beginning of the year at the vernal equinox, Arthur Anthony Macdonell 1917 stated that the twelve intercalary days "in all probability" were inserted at the winter solstice. A.B. Keith 1925 also criticized Tilak's interpretation by pointing to "... the fact that a year of 360 days and 12 months is ... the only year clearly known to the whole of Vedic literarure prior to the late Sutras". Because he also "admits that ancient Indians had knowledge of intercalation" his statements on that point are considered "confused". But already 1895 a similar view in terms of the length of the year was stated by George Thibaut and W.D. Whitney in Indian Antiquity. In 1960 Narendra Nath Law wrote in Indian Antiquity Quaterly that: "W<hitney> would be correct if the 7th season or the 13th month (presumably for intercalation) had not been mentionend." He was referring to RV 1.164.15 which was interpreted by H.H. Wilson as describing seven seasons. But according to the translation of Ralph Thomas Hotchkin Griffith RV 1.164.15 means the seven Rishis, which according to David Frawley were actually eight seers, representing the Big Dipper. The eighth star of the big dipper is according to his later reference to RV 3.56.2 in connexion with RV 1.164.15 not the unseen fourth star of the handle forming a double star system but the Pole Star around which the big dipper rotates. Already Moritz Winternitz 1907 pointed "to the fact that there are certain passages in the Vedic texts which admid of various interpretations." So A.B. Keith's and A.A. Macdonell's 1912 statement is still appplicable, the 12 days were "merely the 'reflexion of the year' (samvatsarasya pratima) in the same way that they represent the twelve months and have no relation to chronology at all."
- Dates and Eras in Ancient Indian History Collection of Articles from the Indian Historical Quaterly compiled by P. Mittal Geeta Dua, Delhi 2010, Vol.1, p.76, Note 83
- suggested in OED
- RigVeda Samhita Vol.I According to the translation of H.H. Wilson and Bhasya of Sayanacarya by Ravi Prakash Arya and K.L.Joshi
- H.H. Wilson The Vishnu Purana A System of Hindhu Mythology And Tradition, Delhi 1980, Reprint 2003, Vol.1 p.366 ff.
- The Song of Ribhu: Translated from the Original Tamil version of Ribhu Gita: Translated by Dr. H. Ramamoorthy and Nome, Published by Society of Abidance in Truth
- Vettam Mani Puranic Encyclopedia, Delhi 1975, 9th Reprint 2010, p.647
- Bal Gangadhar Tilak The Orion, Or, Researches Into The Antiquity Of The Vedas, Reprinted from 1893 Edition Delhi 2008, p.167
- Dates and Eras in Ancient Indian History Vol.1, p.76, Note 85, referring to A. Berriedale Keith Philosophy and Religion of the Veda and Upanishads Vol.1, p.176
- The Orion, p.167
- Dates and Eras in Ancient Indian History Vol.1, p.76, Note 72
- Dates and Eras in Ancient Indian History Vol.1, p.53
- Gods, Sages and Kings, p.169
- The Orion, p.167; Dates and Eras in Ancient Indian History Vol.1, p.51
- Dates and Eras of Ancient Indian History Vol.1, p.76, Note 73
- Dates and Eras in Ancient Indian History Vol.1, p.54
- Dates and Eras in Ancient Indian History Vol.1, p.76, Note 85, referring to A.B. Keith Philosophy and Religion in the Veda and Upanishads Vol.1, p.178
- The Orion, p.113 f.
- Bal Gangadhar Tilak The Orion, p.139
- David Frawley Gods, Sages And Kings, first Indian Edition, Delhi 1993, p.173
- The Orion, p.113 f.
- Gods, Sages And Kings, p.177
- The Orion, p.114, see also p.109
- Gods, Sages And Kings, p.157
- The Orion, p.170
- The Orion, p.169
- Dates and Eras of Ancient Indian History Vol.1, p.52 f., referring to W.D. Whithey in Indian Antiquity
- The Orion, p.169, compare p.115
- The Orion, p.168 f.
- Dates and Eras in Ancient Indian History Vol.1, p. 51
- Dates and Eras in Ancient Indian History Vol.1, p.76, Note 86, referring to A.A. Macdonell A History of Sanscrit Literature, p.106
- Dates and Eras in Ancient Indian History Vol.1, p.56, referring to A.B. Keith Philosophy and Religion of the Veda and Upanishads Vol.1
- Dates and Eras in Ancient Indian History Vol.1, p.57; 56
- Dates and Eras in Ancient Indian History Vol.1, p.56
- Dates and Eras in Ancient Indian History Vol.1, p.57
- Dates and Eras in Ancient Indian History Vol.1, p.57
- Dates and Eras in Ancient Indian History Vol.1, p.55, referring to H.H. Wilson Rigveda (Translation) Vol.2, p.131 f.
- Ralph Thomas Hotchkin Griffith The Hymns of the Rigveda Vol.1, Benares 1889, Reprint USA 2012, p.286
- Gods, Sages and Kings, p.167
- Gods, Sages and Kings, p.172, refer also p.167, the 8th seer
- Dates and Eras in Ancient Indian History Vol.1, p.49, referring to M. Winternitz A History of Indian Literature Vol.1, german 1907, english translation 1927, p.30
- Dates and Eras in Ancient Indian History Vol.1, p.57, referring to A.B. Keith and A.A. Macdonell Vedic Index of Names and Subjects Vol.2 "Samvatsara", p.411-13
- Generally: Monier-Williams, Sanskrit-English Dictionary (1899), s.v. 'ṛbhu'