Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 18
Sanskrit:
तं च ब्रह्मर्षयोऽभ्येत्य हयमेधेन भारत ।यथावद्दीक्षञ्चक्रु: पुरुषाराधनेन ह ॥ १८ ॥
ITRANS:
taṁ ca brahmarṣayo ’bhyetyahayamedhena bhāratayathāvad dīkṣayāṁ cakruḥpuruṣārādhanena ha
Translation:
O King, when Lord Indra reached the heavenly planets, the saintly brāhmaṇas approached him and properly initiated him into a horse sacrifice [aśvamedha-yajña] meant to please the Supreme Lord.