Srimad Bhagavatam Canto 06, Chapter 13, Text 18

SB 6.13.18

tam ca brahmarsayo ’bhyetya
 hayamedhena bharata
yathavad diksayam cakruh
 purusaradhanena ha
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
O King, when Lord Indra reached the heavenly planets, the saintly brahmanas approached him and properly initiated him into a horse sacrifice [asvamedha-yajña] meant to please the Supreme Lord.
Srimad Bhagavatam Canto 06, Chapter 13, Text 17
Srimad Bhagavatam Canto 06, Chapter 13, Text 19-20