SB 6.14.7

atra naḥ saṁśayo bhūyāñ
 chrotuṁ kautūhalaṁ prabho
yaḥ pauruṣeṇa samare
 sahasrākṣam atoṣayat
atra — in this connection; naḥ — our; saṁśayaḥ — doubt; bhūyān — great; śrotum — to hear; kautūhalam — eagerness; prabho — O my lord; yaḥ — he who; pauruṣeṇa — by bravery and strength; samare — in battle; sahasra-akṣam — Lord Indra, who has one thousand eyes; atoṣayat — pleased.
My dear lord, Śukadeva Gosvāmī, although Vṛtrāsura was a sinful demon, he showed the prowess of a most exalted kṣatriya and satisfied Lord Indra in battle. How could such a demon be a great devotee of Lord Kṛṣṇa? These contradictions have caused me great doubt, and they have made me eager to hear of this from you.