"This is the Torah (the teaching) regarding a man who dies in a tent..." (Chukas 19:14). Chazal (Brachos 63b) interpret this posuk homiletically to mean that words of Torah make a lasting impression only on one who figuratively "kills" himself in the tent of study. The Taz (Orach Chaim 46:1) explains that this refers to someone who exerts much effort and toil (ameilus) to understand the depths of Torah. At first glance, this statement of Chazal seems puzzling. Studying Torah with extraordinary ameilus is certainly praiseworthy. But why should investing effort to understand the Torah automatically lead to a better retention of the Torah that is studied?
The Mishna (Avos 6:1) states, "Reb Meir says that one who engages in the study of Torah for its own sake (lishma) merits many things." The first of these is that he is called a rei'ah ahuv (beloved friend) of Hashem and the Torah. What does it mean to be a "beloved friend"? Reb Chaim of Volozhin (Ruach Chaim, ibid) suggests that there are two types of friendships. Some friendships are formed out of selfish considerations. A person might want to benefit from another's wealth, services, or position of prominence, or he might simply want to feel the honor of being the friend of such a distinguished individual. Such a friendship is not deeply rooted and sincere; it is superficial and utilitarian, and will last only as long as it remains beneficial for the parties involved. About such a relationship Shlomo HaMelech warns, "Do not frequent your friend's home too often lest he become satiated with you and he will hate you" (Mishlei 25:17). When a friendship is pursued for the sake of convenience, there is always the concern that the other individual might feel that he is being taken advantage of, and the relationship might sour. Maintaining a healthy distance is key to preserving such a relationship.
But there is a second type of friendship, and that is one which is based on mutual respect and admiration. Such a relationship is enduring because it is motivated not by selfish concerns but by an appreciation of the character and the inherent qualities of the other person. Friends of this type enjoy each other's company and the more time they spend together the stronger the bonds between them become. This is what Reb Meir refers to as a "beloved friend". When someone appreciates the value of his friend and he cherishes their relationship for its own sake, he becomes beloved in the eyes of his friend, and the friend will reciprocate that love in return.
Reb Chaim of Volozhin explains that this is why a chosson and kallah are referred to as reiyim ahuvim (beloved friends) because the ideal marriage relationship is one in which the husband and wife are not looking to advance their own interests, but rather are willing to sacrifice of themselves for the benefit of the other. Such a relationship which is based on mutual respect and selflessness will only strengthen over time and will make each person more beloved in the eyes of the other. Similarly, one who engages in Torah study not to receive honor or to make a living, but rather for the sake of the Torah itself is called a "beloved friend" of the Torah and of Hashem because through his learning he demonstrates his unconditional love for the Torah, and in return the Torah and Hashem love him as well.
Perhaps this is the deeper meaning behind the statement of Chazal that words of Torah make a lasting impression only if one "kills" himself in studying them. The more effort a person invests in Torah study and the more he is willing to sacrifice in order to learn Torah, the more he demonstrates his love for the Torah, and that emotional bond which he develops with the Torah will cause him to remember the Torah that he studied. Moreover, when a person shows his love for the Torah, the Torah and Hashem reciprocate that love, and the individual is blessed with extra special powers of retention. As Chazal comment (Eiruvin 54a) on a later posuk in Parshas Chukas (21:18) "'And a gift from the desert' - one who makes himself ownerless (hefker) like a desert...will remember his Torah." One who sacrifices his own needs and selflessly pursues the study of Torah receives an extra gift of Torah. He is blessed with additional siyata dishmaya (divine assistance), and that enables him to retain his Torah more easily.
Hard work and effort are necessary prerequisites to acquire any type of knowledge. But when it comes to the study of Torah these ingredients pay extra dividends.