The first aliyah (section) of Parshas Mishpatim discusses the mitzva of eved ivri (Jewish slave). If an eved ivri decides that he would like to work for his master after his term has ended, he has his ear pierced beside a doorpost. There is much significance in the fact that his ear is pierced, as the ear represents listening and absorbing the wisdom we hear from others. When we accepted the Torah, the real acceptance came from our agreeing to keep the mitzvos even before we heard what Hashem demands from us. The eved's ear is pierced as a reminder that he is choosing to listen to a human master instead of Hashem. We have a resistance to the concept of servitude to a human because we want to exclusively hear the call of Ol Torah (yoke of Torah), to ensure that we are doing only that which Hashem wants.