We commonly respond to requests to pray on other people's behalf. A friend or perhaps simply an acquaintance will ask us to daven for his friend or relative who is ill, undergoing surgery, and the like. We submit names for such individuals and the gabbai makes a mi shebeirach on their behalf. Commonplace, benevolent practices that we take for granted, and yet the basis for such prayer needs to be elucidated. Maharal, in his Nesiv Ha'avodah chapter twelve, questions the admissibility of such prayer. Maharal opines that possibly one can not pray exclusively on behalf of others, as we ostensibly regularly do in the above scenarios.
At first glance, Maharal's position is very puzzling. Must tefillah be self-centered? Moreover, does not the Torah provide examples of such altruistic prayer - Avraham Avinu on behalf of Avimelech and his household and the people of Sedom, Moshe Rabbeinu on behalf of Miriam and consistently for Bnai Yisroel?
In order to understand and appreciate the beauty of Maharal's position we must first understand the gift and obligation of prayer. Rambam in defining the mitzvah of tefillah writes that after reciting the praise of HKB"H, "sho'el tzrachav she'hu tzarich lahen". Translated literally if unidiomatically, "a person asks for his needs that he needs". Now admittedly Rambam's formulation in the original Hebrew does not grate as it does in the clumsy English translation, but the apparent redundancy is definitely present in Rambam's own words. In truth, of course, there is no actual redundancy. Rambam is expressing that in order to pray one must experience need. One must feel needy, dependent. It does not suffice for a person to know intellectually that he has tzrochim (needs). He must feel those needs in order to daven ("hu tzarich lahein") for this is an indispensable element of prayer - turning to HKB"H out of a sense of need, dependence and vulnerability. An individual who feels smug and self-sufficient can turn pages in the prayer book and mouth all the words; but he can not pray.
Operating with Rambam's beautiful, religiously sensitive definition of she'eilas tzrochim (request, petition) within prayer, we can appreciate the position of the Maharal. It is not that tefillah should be self-centered; self-centeredness is not a virtue. But tefillah must emanate from a sense of need. If one does not experience need, he can not pray. Hence, one can not with a sense of detachment pray exclusively for another individual's needs.
But the second question remains. Avraham Aivnu did so, Moshe Rabbeinu did so. The answer lies in a famous story about the tzaddik of Yerushalayim, Reb Aryeh Levin. He once accompanied his wife who was experiencing pain in her knee to a doctor. Explaining the reason for the visit he told the doctor, "our knee hurts." Reb Aryeh Levin's sense of empathy was such that he experienced his wife's (and other people's) needs as his own.
This empathetic experience, says the Chasam Sofer by way of explaining the Maharal (responsa Orach Chaim 166), allows us to daven on behalf of others. When, with love and compassion, we experience their needs as our own we are able to daven on their behalf. Avraham Aivnu did so, Moshe Rabbeinu did so, and it is our challenge to do so as well!