Ambarvalia
Ambarvalia was a Roman agriculture-fertility rite held on the 29th of May to honor Ceres, goddess of grain, crops, harvest, agriculture, motherly relations, etc., and Dea Dia, goddess of fertility and growth.
At the festival, a bull, a sow, and a sheep were led in procession thrice around the fields, and then sacrificed. There were also feasts, public and private ones. Private feasts were celebrated by the masters of the families, and they’d be accompanied by their children and servants in farms and villages out of Rome. Public feasts were celebrated within the city. Twelve fratres arvales would walk at the head of a ‘parade’ of citizens.
During this procession, prayers would be made to the goddess(es). The ambervale carmen was a preferred prayer at this time.
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