The great saint Dadhici had perfect knowledge of how to perform fruitive activities, and he had advanced spiritual knowledge as well. Knowing this, the Asvini-kumaras once approached him and begged him to instruct them in spiritual science (brahma-vidya). Dadhici Muni replied, I am now engaged in arranging sacrifices for fruitive activities. Come back some time later. When the Asvini-kumaras left, Indra, the King of heaven, approached Dadhici and said, My dear Muni, the Asvini-kumaras are only physicians. Please do not instruct them in spiritual science. If you impart the spiritual science to them despite my warning, I shall punish you by cutting off your head. After warning Dadhici in this way, Indra returned to heaven. The Asvini-kumaras, who understood Indras desires, returned and begged Dadhici for brahma-vidya. When the great saint Dadhici informed them of Indras threat, the Asvini-kumaras replied, Let us first cut off your head and replace it with the head of a horse. You can instruct brahma-vidya through the horses head, and when Indra returns and cuts off that head, we shall reward you and restore your original head. Since Dadhici had promised to impart brahma-vidya to the Asvini-kumaras, he agreed to their proposal. Therefore, because Dadhici imparted brahma-vidya through the mouth of a horse, this brahma-vidya is also known as Asvasira.