[O]k skyldi þeim gelti blóta at sónarblóti. Jólaaptan skyldi leiða sónargöltinn í höll fyrir konúng; lögðu menn þá hendr yfir burst hans ok strengja heit.
[A]nd they would sacrifice a boar in the sonarblót. On Yule Eve the sonar-boar was led into the hall before the king; then people laid their hands on its bristles and made vows.
Um kveldit [jólaaftan] óru heitstrengingar. Var fram leiddr sónargöltr. Lögðu menn þar á hendr sínar ok strengðu menn þá heit at bragarfulli.
That evening [of Yule Eve] the great vows were taken; the sacred boar was brought in, the men laid their hands thereon, and took their vows at the king's toast.
The association with the Yule blót and with the ceremonial bragarfull gives the vows great solemnity, so that they have the force of oaths. This becomes a recurring topos in later sagas, although we have only these two saga mentions attesting to the custom of making vows on the sacrificial animal.
The choice of a boar indicates a connection with Freyr, whose mount is the gold-bristled boar Gullinbursti, and the continuing Swedish tradition of eating pig-shaped cakes at Christmas recalls the early custom. According to Olaus Verelius' notes in his 1672 edition of Hervarar saga ok Heiðreks, part of this jula-galt would then be saved for mixing with the seed-corn and giving to the plough-horses and ploughmen at spring planting. As Jacob Grimm pointed out, the serving of a boar's head at banquets and particularly at Queen's College, Oxford may also be a reminiscence of the Yule boar-blót. Gabriel Turville-Petre suggested that names for Freyr and his sister Freyja which equate them with a boar and a sow respectively implied that consumption of the sacrificed boar was believed to be consumption of the god's flesh and absorption of his power.
It was formerly usual to spell the word sónargǫltr and to interpret it as "atonement-boar" (the rare element sónar- can also mean "sacrifice"). However, following Eduard Sievers, it is usually now spelled with a short o and taken as meaning "herd boar, leading boar", as Lombard sonarþair is defined in the Edictus Rothari as the boar "which fights and beats all other boars in the herd".
- Saga Heiðreks konungs ins vitra, H-text of Hervarar saga ok Heiðreks, chapter 10, from Heimskringla.no. Note that this text uses the sónar spelling.
- For the alternate version, in which the procedure is the same but the word sonargǫltr does not occur, see Richard North, Heathen Gods in Old English Literature, Cambridge Studies in Anglo-Saxon England 22, Cambridge, 1997, ISBN 978-0-521-55183-0, p. 74.
- "Helgakviða Hjörvarðssonar", prose before verse 31, Old Norse and Henry Adams Bellows' translation from voluspa.org. Again the sónar spelling is used.
- "Sonargǫltr", Rudolf Simek, Dictionary of Northern Mythology, tr. Angela Hall, Cambridge: Brewer, 1993, repr. 2000, ISBN 978-0-85991-369-0, p. 298.
- Jan de Vries, Altgermanische Religionsgeschichte, Volume 1, Grundriß der germanischen Philologie begründet von Hermann Paul 12/I, 2nd ed. Berlin: De Gruyter, 1956, repr. as 3rd ed. 1970, OCLC 747429, p. 367 (in German)
- de Vries, p. 504.
- Peter Habbe, Att se och tänka med ritual: kontrakterande ritualer i de isländska släktsagorna, Vägar till Midgård 7, Lund: Nordic Academic Press, 2005, ISBN 9789189116795, p. 43 (in Swedish)
- Ruth Schmidt-Wiegand points to a prohibition in the Salic law that suggests the Franks sacrificed only the generative organs of the boar to the fertility god Freyr, reserving the rest for the feast: "Spuren paganer Religiosität in den frühmittelalterlichen Leges", in Iconologia sacra: Mythos, Bildkunst und Dichtung in der Religions- und Sozialgeschichte Alteuropas: Festschrift für Karl Hauck zum 75. Geburtstag, ed. Hagen Keller and Nikolaus Staubach, Arbeiten zur Frühmittelalterforschung 23, Berlin: De Gruyter, 1994, ISBN 978-3-11-013255-7, pp. 249–62, pp. 256–57 (in German)
- Jacob Grimm, Teutonic Mythology, tr. James Steven Stallybrass, Volume 1, London: Bell, 1882, p. 51.
- H. F. Feilberg, Jul, volume 2, Copenhagen: Schuboth, 1904, pp. 313–14 (in Danish)
- Helge Rosén, "Freykult och Djurkult", Fornvännen 1913, pp. 213–44, pp. 214–15, pdf (in Swedish)
- Grimm, Volume 3, 1883, p. 1240.
- Grimm, Volume 1, p. 215; Volume 4, 1883, p. 1355.
- Rosén, p. 214.
- Ernst Anton Quitzmann, Die heidnische Religion der Baiwaren: erster faktischer Beweis für die Abstammung dieses Volkes, Leipzig: Winter, 1860, OCLC 252676776, p. 86 (in German) notes that Bavarian farmers feasted on a slaughtered pig at Yule.
- E. O. G. Turville-Petre, Myth and Religion of the North: The Religion of Ancient Scandinavia, London: Weidenfeld, 1964, OCLC 645398380, p. 255; Habbe wrongly sees this as referring to a bear sacrifice.
- "Són", An Icelandic-English Dictionary, initiated by Richard Cleasby, subsequently revised, enlarged, and completed by Gudbrand Vigfusson, 2nd ed. with supplement by William A. Craigie, Oxford: Oxford/Clarendon, 1957, repr. 1975, ISBN 978-0-19-863103-3, p. 580, online at Germanic Lexicon Project.