One of the problems that many theologians have grappled with is: "Why and how does prayer work?" If a sick person prays for recovery, he is assuming that God has allowed him to become sick. Is he to believe that his prayer can make God change His mind?
One of the answers given is that there is a constant outpouring of Divine benevolence to the world. Just as the sun radiates light, yet there are areas of darkness in enclosures where the sunlight does not reach, so does the Divine benevolence not reach where there are barriers that obstruct it. These barriers are a person's actions that are contrary to the will of God.
Genuine, sincere prayer brings a person into a closer relationship with God. The barriers to the Divine benevolence are thereby removed or circumvented, and the person can then receive this benevolence. The blessing and improvement in the person's health is not the result of a change in God's will, but of a change in the status of the recipient.
This is similar to Maimonides' explanation for the effectiveness of teshuvah (repentance). Teshuvah is not merely regretting a wrong that one has done. Rather, teshuvah consists of a person realizing how and why he came to commit a sin, and to advance himself spiritually so that it would be impossible for him to commit that sin if the same circumstances and temptation recurred. This amounts to a significant change in one's character. The person who has done proper teshuvah is now a new person. His personality has changed and he is not the same person who committed the sin. It is, therefore, justified that this newly emerged person not be held responsible for the actions of the previous person.
This also applies to the effectiveness of prayer. Genuine prayer brings about a transformation in a person. The newly emerging person can be receptive of the Divine benevolence to which the former person was impervious.
PRAYING FOR OTHERS
This may explain why a person's prayer in his own behalf is effective. But why is it effective when one person prays for another person? The Talmud says that if a member of the family is sick, "let him go to a Torah scholar and ask him to pray for him." In this case, the sick person is not undergoing a character transformation that would make him a new person. How can the scholar's prayer cause God to change His mind?...
We can further understand why prayer may be effective even though God does not change His mind.
For reasons known only to God, Divine justice may decree that a particular person must undergo suffering. This person shares his pain with a friend, who is so moved by his friend's distress that he suffers along with him and prays for him. However, Divine justice never decreed that the second person suffer. Therefore, in order to relieve the friend from unwarranted suffering, Divine justice requires that the first person be relieved of his distress.
The concern for the friend's suffering must be sincere. This is why the Talmud says that if one prays on another person's behalf rather than pray for himself, his own prayers are answered quickly.
STIMULUS FOR GROWTH
Rabbi Yechezkel Levenstein says that sometimes a person is given distress to stimulate him to pray. He bases this on the Midrash which states that the reason the Patriarchs and Matriarchs were barren for so lengthy a time was because God desired their prayers.
God has no selfish motivation. The reason he wished the Patriarchs and Matriarchs to pray is because prayer elevates a person spiritually.
The Talmud says that had we not been given the Torah, we would have been obligated to learn proper life habits from the observation of God's creatures. Perhaps we would have learned something about growth from the observation of lobsters.
A lobster is a soft animal that resides within a rigid, inflexible shell. As it grows, the shell becomes very confining. When it becomes oppressive, the lobster retreats to an underwater rock formation where it is safe from predatory fish, sheds its shell, and forms a larger, more spacious one. Eventually this new shell becomes oppressive as the lobster continues its growth, and the process is repeated several times until the lobster reaches its maximum size.
The stimulus for the lobster to throw off its restraining shell so that it may grow is discomfort. This may be true for human beings as well. If we are comfortable, we are unlikely to do anything to advance ourselves. The greater the discomfort, the greater is the stimulus for growth. The Patriarchs and Matriarchs' desire for offspring was so intense that they were moved to profound prayer. It was this intensity of prayer that elevated them to such lofty spirituality.
This is further borne out by the Midrashic statement that after the ordeals of Esau, Laban and Dinah, the patriarch Jacob wished to live in tranquility. God said, "Tranquility is reserved for the eternal world," and Jacob was subjected to the suffering of the loss of his beloved son, Joseph. It is not that God wishes to deny anyone tranquility, but that tranquility is not conducive to spiritual growth. The latter is catalyzed by distress.
Rabbi Levenstein explains that inasmuch as the purpose of distress is to stimulate a person to prayer, it is only logical that when this purpose is achieved, the distress disappears.
[And thus we see how] prayer is effective, whether we pray for ourselves or for others.
Reprinted with permission from InnerNet.org and excerpted with permission from "TWERSKI ON PRAYER" - creating the bond between man and his maker. Published by Shaar Press, distributed by Mesorah Publications Ltd.