Honoring ones Parents

The מצוה of כיבוד אב ואם is mentioned in the middle of עשרת הדיברות, between the מצוות that are בין אדם למקום and the מצוות that are בין אדם לחברו chazal say 3 שותפים באדם. The reason maybe that it is considered in both catagories is because normally the מצוות בין אדם לחברו are part if a normal social contract but one is not obligated to allow himself to be abused. As the blind man said when people were helping him "it's nice that they are helping me but I am not a לו לב, meaning treat me nice because I'm another human being not because I am a "חפץ של מצוה". However, a parent is actually like a לולב, he IS a חפץ של מצוה. A child IS obligated to take abuse from his parent and that obligation is aבין אדם למקום obligation.