Rigvidhana 3.26

During the bright fortnight, on an auspicious day, under an auspicious lunar mansion, in an auspicious planetary position, / on the twelfth day, for the desire of a son, one should prepare a cooked mess of grain for Viṣṇu.

There should be fasting for the husband and wife on the eleventh day in a clean house. / Having worshipped Janārdana properly with the sixteen verses,

he should cook the cooked mess of grain with the Puruṣa hymn with the desire for a son. / He will soon obtain a son devoted to Viṣṇu, capable of continuing the lineage.

One who properly prepares the cooked mess of grain with milk on twelve twelfth days, / if he performs it a thousand times, he goes to the supreme abode of Viṣṇu.

Having offered into the fire according to rule properly with the sixteen verses, the wise man, / having joined his hands in reverence, should employ praise with them.