SB 6.13.19-20

athejyamāne puruṣe
 sarva-devamayātmani
aśvamedhe mahendreṇa
 vitate brahma-vādibhiḥ
sa vai tvāṣṭra-vadho bhūyān
 api pāpa-cayo nṛpa
nītas tenaiva śūnyāya
 nīhāra iva bhānunā
Word for word: 
atha — therefore; ijyamāne — when worshiped; puruṣe — the Supreme Personality of Godhead; sarva — all; deva-maya-ātmani — the Supersoul and maintainer of the demigods; aśvamedhe — through the aśvamedha-yajña; mahā-indreṇa — by King Indra; vitate — being administered; brahma-vādibhiḥ — by the saints and brāhmaṇas expert in Vedic knowledge; saḥ — that; vai — indeed; tvāṣṭra-vadhaḥ — the killing of Vṛtrāsura, the son of Tvaṣṭā; bhūyāt — may be; api — although; pāpa-cayaḥ — mass of sin; nṛpa — O King; nītaḥ — was brought; tena — by that (the horse sacrifice); eva — certainly; śūnyāya — to nothing; nīhāraḥ — fog; iva — like; bhānunā — by the brilliant sun.
Translation: 
The horse sacrifice performed by the saintly brāhmaṇas relieved Indra of the reactions to all his sins because he worshiped the Supreme Personality of Godhead in that sacrifice. O King, although he had committed a gravely sinful act, it was nullified at once by that sacrifice, just as fog is vanquished by the brilliant sunrise.