vainye yajna-pasum spardhann
caramena—by the last one; asva-medhena—by the asvamedha sacrifice; yajamane—when he was performing the sacrifice; yajuh-patim—for satisfaction of the Lord of yajna, Visnu; vainye—the son of King Vena; yajna-pasum—the animal meant to be sacrificed in the yajna; spardhan—being envious; apovaha—stole; tirohitah—being invisible.
When Prthu Maharaja was performing the last horse sacrifice [asvamedha-yajna], King Indra, invisible to everyone, stole the horse intended for sacrifice. He did this because of his great envy of King Prthu.
King Indra is known as sata-kratu, which indicates that he has performed one hundred horse sacrifices (asvamedha-yajna). We should know, however, that the animals sacrificed in the yajna were not killed. If the Vedic mantras were properly pronounced during the sacrifice, the animal sacrificed would come out again with a new life. That is the test for a successful yajna. When King Prthu was performing one hundred yajnas, Indra became very envious because he did not want anyone to excel him. Being an ordinary living entity, he became envious of King Prthu, and, making himself invisible, he stole the horse and thus impeded the yajna performance.
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