Suovetaurilia

The suovetaurilia or suovitaurilia was one of the most sacred and traditional rites of Roman religion: the sacrifice of a pig (sus), a sheep (ovis) and a bull (taurus) to the deity Mars to bless and purify land (Lustratio).

The ritual is preserved in Cato the Elder's De Agri Cultura, "On Agriculture". The first step was to lead the three animals around the boundaries of the land to be blessed, pronouncing the following words:

"Manius" in this passage may be an obscure minor deity, related to the Manes, or may be the equivalent of English John Doe. Then, before the sacrifice is performed, the following prayer to Mars must be made:

The original Latin of this prayer is crudely metrical and incantatory; even in Old Latin, the prayer contains many rhetorical figures such as alliteration and liberal use of merisms and antithesis. It illustrates the sing-song, metrical, and poetic format of polytheistic prayers. Cakes of bread were sacrificed along with the three animals. At the moment the sacrifices were made, the landowner was to say:

If favourable omens as a response to the sacrifice were not forthcoming, the landowner was instructed to redo the sacrifice and offer a further prayer:

If only one or two of the omens expected after the three sacrifices failed to appear, the landowner was instructed to offer an additional swine, saying:

The nature of the expected omens is not given by Cato. The omens, however, were likely determined by the art of haruspicy, the examination of the entrails, and especially the livers, of sacrificed animals for divinatory signs.

...
Wikipedia