In this week's Parsha, the Torah says, that Yaakov asked Yosef to deal kindly with him after his death, and should not bury him in the land of Egypt (בראשית מ"ז:כ"ט). Yaakov describes this act of kindness as an act of חסד ואמת, which literally means kindness and truth. Rashi (שם בד"ה חסד) explains that this is an example of true kindness, because it is being done for someone who is dead. The person will obviously not ever be able to repay that act of kindness; the act is therefore an act of kindness and truth, because it is done for no reason other than to demonstrate pure and true kindness.
The Ohel Yaakov, however, offers a slightly different interpretation. He states that when dealing kindly with a person while he is alive, one does not know whether that act is truly an act of kindness or not. Sometimes, what one may think is an act of kindness might actually result in harm and cause suffering for that person. The mercy shown to the dead, however, is always true kindness because this loving kindness can not result in harm for that person. Furthermore, when an individual does a kindness to a living person, there can be other motivations, such as the desire for a reward, but when it comes to kindness to the dead, there is not a chance of thanks or a reward from that person. It is perhaps for this reason that taking care of a מת מצוה, a dead body which has no one to take care of it, is such an important Mitzvah that even a Kohein is allowed to become טמא, ritually impure, to fulfill this Mitzvah, because this is true kindness, and this is what the Torah wants of us.