Source : http://www.thehindu.com/society/faith/brahma-jnana-is-the-key/article18420834.ece
Are all people who know the Vedas certain to attain moksha?
This is a question Lord Krishna answers in the Bhagavad Gita. He says that there may be persons well versed in the rituals prescribed in the Vedas. They may, therefore, know how to perform yagas. But if they are unfamiliar with the Upanishads, that means they lack Brahma jnana. Therefore, they do not know that even when other gods like Indra are being propitiated through yagas, it is only the Supreme One, Lord Narayana, who gives the benefits of the sacrifices.
So will they not get any benefits by performing the yagas? Whatever benefits are assured through performance of a yaga will come to them, said Valayapet Ramachariar in a discourse. A portion of their sins also gets destroyed. But the rest of their sins remain. Because of acquiring some merit through a yaga, they go to svarga. But after some time, they are again born on this earth. They may do more yagas and go many more times to svarga, but each time they have to come back when their merits have been exhausted. That is why Lord Krishna says, gata agatam labhante — they keep coming and going and suffering.
If a person knows that the Supreme One is in charge of everything, he will not seek petty things in life. His only aspiration will be to attain moksha. But he who does not know Him will keep performing sacrifices and seeking other ways of pleasing Indra and other gods, none of whom has the power to grant moksha.
In his Varadaraja stavam, Kooratazhvan says that if one goes round Lord Varadaraja of Kanchipuram once, it will become clear that He is the Supreme One. The Vedas, it is true, reveal Him, but they will do so only to the one who has understood the Upanishads and not merely the ritual portion of the Vedas.