Extract : Vedas do not conceive of a God or Paramatma who would change his course of actions even a bit to accommodate our prayers. Then what is the use of such prayers or innumerable similar ones, which He would never listen to?
The fact however remains that Vedas contain no prayer which is impossible. The mechanism of action of Vedic prayers is already built into our system. Paramatma has already supplied us with all necessary arms and ammunition to achieve whatever we desire within the framework of Vedas. The Vedas provide the tools and techniques to use these arms and ammunition and convert any of our prayers into reality. We perform, and he dispenses – as per definite unchangeable laws, as provided in the Vedas.

Q. As per this , is it useless to do yagna for a deceased's soul ?