Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 15-16
Sanskrit:
स सन्नद्धो धनुर्दिव्यमादाय विशिखाञ्छितान् ।स्तूयमानस्तमारुह्य युयुत्सु: ककुदि स्थित: ॥ १५ ॥तेजसाप्यायितो विष्णो: पुरुषस्य महात्मन: ।प्रतीच्यां दिशि दैत्यानां न्यरुणत् त्रिदशै: पुरम् ॥ १६ ॥
ITRANS:
sa sannaddho dhanur divyamādāya viśikhāñ chitānstūyamānas tam āruhyayuyutsuḥ kakudi sthitaḥ
Translation:
Well protected by armor and desiring to fight, Purañjaya took up a transcendental bow and very sharp arrows, and, while being highly praised by the demigods, he got up on the back of the bull [Indra] and sat on its hump. Thus he is known as Kakutstha. Being empowered by Lord Viṣṇu, who is the Supersoul and the Supreme Person, Purañjaya sat on the great bull and is therefore known as Indravāha. Surrounded by the demigods, he attacked the residence of the demons in the west.