"The Parilia, as we know it, was essentially a rite of purification which involved the cleansing of sheep and sheep-folds, and the leaping of celebrants over fires of burning bean-straw. Certain februa or purifying agents were used in the ceremony, viz. beanstraw, blood from the October Horse, and the ashes of unborn calves taken from cows slaughtered at the Fordicidia. Among the offerings were cakes of millet and warm milk, and milk was drunk by the worshippers before leaping the flames (Ovid, Fasti 4. 721 ff.)."Ovid describes Parilia in the fourth book of his Fasti.
Natalis urbis and Principium anni"
Van L. Johnson
Transactions and Proceedings of the American Philological Association, Vol. 91 (1960), pp. 109-120.
Source: Adkins and Adkins Handbook of Life in Ancient Rome