A Rabbi's Blessing

Q: How does the blessing of a Rabbi work?
A: There is obviously also a question on a person's prayer for himself. How can a person pray to Hashem? Does he expect to change Hashem's will? The Rivash explained this idea with a parable. A king said to one of his officers: "This man committed a crime against me, put him in prison. But if you come to arrest him and he asks forgiveness, let him go." When the criminal pleads for mercy, he does not change the king's mind. The king's will was if he acts this way, he will be forgiven. Hashem sometime decides if a person prays it will be one way, and if he does not it will be another way. Furthermore, the reason one person can pray for another is based on the idea that certain souls are unified. I can therefore pray for my son or brother. Regarding a Torah scholar, the Gemara says that it is as if everyone is his relative (see Moed Katan 25a and other places). The prayer has the potential to help him if one is not merely saying words, but truly means it.