The eleventh mantra in Apratiratha Sukta uses the word Vritrahan. Commentator Sayanacharya explained Vritrahan as referring to Indra, who killed Vritrasura. But the Vedas use the word Vritra in a broader sense. If one goes into the details seen in the Vedas, then it becomes clear that this eleventh mantra is a prayer to Vishnu, said V.S. Karunakarachariar in a discourse. Taittiriya Samhita describes Indra’s battle with Vritrasura. Here it is said that Indra worshipped Vishnu, who stood in three places during the battle with Vritrasura. Indra takes Vritrasura’s possessions in three instalments, and offers them to Vishnu. Vritrasura then enters Indra’s body and takes the form of hunger.
Vritrasura can be vanquished by the weapon known as Vajra. The vajra that vanquishes hunger is the power of yagas. That is why it is said: vajrovai yajnah. So Vritrasura is a symbolic representation of hunger, with which we are born and which stays with us till the end. Vritrasura is also portrayed as the embodiment of sins. When yagas are performed, there is a prayer for the destruction of Vritrasura. This is a prayer for the destruction of our sins. Lord Krishna is the One capable of doing this.
In the Bhagavad Gita, Lord Krishna says sarva papebhyoh mokshayishyami. So, here He guarantees the destruction of all the sins of those who surrender at His feet. He also assures His devotees that He will grant them moksha, the only condition being that they wholeheartedly resort to Saranagati.