כבד את אביך ואת אמך
The Sefer Hachinuch explains that the shoresh, root, of the mitzvah of Kibbud Av v’Eim, honoring parents, is a sense of hakoras hatov, gratitude, to those who have acted kindly towards him. One who is a kafui tov, ingrate, is a naval, abominable person. He acts as if his benefactor, in this case his parents, are strangers to him. He quickly ignores the fact that his parents are the reason that he is here altogether. For this alone, he should honor them. One who does not honor his parents will soon present a similar attitude toward his Father in Heaven….