This week’s Parsha teaches the Mitzvah of fearing one's parents, as the Pasuk states (19:3), “Ish Imo VeAviv Tira'u," "A man shall fear his father and his mother." How does one fulfill this Mitzvah? The Sifra explains that one should not sit in his parent's seat or contradict his or her words in a conversation. The Gemara (Kiddushin 31a) says that even if a parent hits a child or spits in the child's face, the child cannot stop his parent's actions. The root of this Mitzvah is showing appreciation for parents and being Makir Tov for all the actions our parents do on our behalf.
A famous story related in the same Gemara illustrates this point. In the time of the second Beit Hamikdash, the Rabbis were looking to find a replacement for one of the precious stones of the Choshen (each stone was worth a great amount of money). The Rabbis approached a non-Jew who was known to have this stone in order to buy it from him. When they arrived, the non-Jew refused to sell them the stone, even for a great profit, because his father was sleeping on top of the key which opened the safe in which the stone was kept. The non-Jew was awarded the following year with the birth of a Parah Adumah, which he was able to sell for a high price. He thus regained his losses for not selling this stone.
As this story clearly demonstrates, one should always be Makir Tov to everyone, especially one's parents, even at a great cost. We must realize that whatever we have to give up to thank our parents is incomparable to the great debt that we owe them for all they have done for us.