Why does the Torah place the Mitzvah of Kibud Av va'Em here?
Ramban: After concluding the Mitzvos she'Bein Adam la'Makom, the Torah moves on to those that are Bein Adam la'Chavero, starting with Kibud Av 1 - since Hashem is one's first Father, and the one who partners Hashem in bringing him into this world, his second father. 2
Seforno: Because it belongs to the group of Mitzvos that are connected with honoring Hashem. 3
Hadar Zekenim: Even though I commanded to honor only Me (and not other gods), honor your father and mother who brought you to this world, and bestowed good on you. If you honor them, who brought you to temporary life, all the more so you will honor Me, who did Chesed with you to bring you to eternal life!
Maharal (Tiferes Yisrael 41): Just like Shabbos shows that Hashem created the world, and it is not chance, also your existence is not chance; you must honor parents [for Hashem decided that you be born to them 4 ].
That is why the Torah in Devarim (5:16) intimates that just as one is Chayav to honor Hashem, so too, is one Chayav to honor one's father (and mother). And that is why the Gemara says in Kidushin 30b) that the Kavod of one's parents is compared to that of Hakadosh-Baruch-Hu (Ramban).
Michtav me'Eliyahu (5, p. 424): There are two primary powers in man
Why does the Torah place Av before Eim here (in connection with Kavod), and Eim before Av in Kedoshim (in connection with Mora)?
Rashi (in Vayikra 19:3): Because knowing that a person tends to honor his mother (who spoils him) more than his father, and to respect his father (who teaches him Torah) more than his mother, Hashem placed the mother first here and the father first there, to counter one's natural inclination - to honor one's father no less than his mother and to respect one's mother no less than his father.
What is the difference between the Mitzvah of Kibud Av va'Em and Mora Av va'Em?
Rashi (Vayikra 19:3): 'Kibud' entails providing them 1 with food and drink and with clothes and shoes, accompanying them out and accompanying them in. 'Mora' entails not sitting in their places and not contradicting their words.
Ramban: 'Kibud' entails honoring them as one honors Hashem 2 - acknowledging that one's father is indeed his father and serving him, not for the anticipated inheritance or for some other ulterior motive, but because he is one's father. Nor may one mention one's parents' names in vain or swear by them in vain or falsely. And there are other things that are listed in Kidushin (31b). 3
What can we learn from the words "Lema'an Ya'arichun Yamecha ... "?
Rashi: We can infer that someone who does not honor his parents will not live long. 1
Ramban #1: The Pasuk teaches us that the reward for Kibud Av va'Em is long life in Eretz Yisrael and in the World to Come. 2
Ramban #2 (based on the Pasuk in Va'eschanan): Long life and having it good on the land are two separate rewards - long life in the World to Come, and having it good in Eretz Yisrael in this world. 3
Seforno: The reward of long life actually pertains to all five of the above-mentioned Dibros. 4
Hadar Zekenim: If you honor them, they will pray for you [and you will live a long life].
Ibn Ezra, Ohr ha'Chayim: It does not say that Hashem will give this for a reward. Rather, this Mitzvah itself is a Segulah for long life! 5
As the Torah's words are subject to inference - negative from the positive and positive from the negative (Rashi).
Because Kibud Av va'Em is one of the Mitzvos which is mainly rewarded in Olam ha'Ba, but the fruit of which is rewarded in Olam ha'Zeh (Kidushin, 40a).
The Gemara there, on Daf 39b however, maintains that long life refers specifically to long life in the World to Come - and that there is no basic reward for Mitzvos in this world (See Torah Temimah, Devarim (5:15, note 5).
Since they are all manifestations of Hashem's Kavod (Bein Adam la'Makom) in thought, word and deed, which earn a person longevity in Eretz Yisrael (See Seforno). Refer also to 20:12:1:1*. And this is why they are all contained on the first Lu'ach. The Ramban on Pasuk 13 (Refer to 20:13:5:1), agrees in principle that Kibud Av va'Em belongs to the Mitzvos bein Adam la'Makom on the first Lu'ach. Refer also to 12:12:1:1.
Michtav me'Eliyahu (5, p. 424): Every person has his share to reveal of Kevod Hashem. Sometimes revelations of relatives must be joined. Kivud Av v'Em mandates extra years to express this.
What is the significance of "al ha'Adamah ... "?
Seforno: Longevity in Eretz Yisrael is the reward that is due for keeping the five Dibros. 1
On the other hand, keeping the remaining five Dibros - which entail not harming one's fellow-Jew, bodily, in his self-esteem or monetarily, in deed, in speech or in thought (Bein Adam la'Chavero) shield one against punishment in both worlds (Seforno).
Rashi (Vayikra 19:3) writes that one may not contradict his parents' words. We find that Rebbi and R. Elazar b'Ribi Shimon contradicted their fathers!
Moshav Zekenim: They disagreed respectfully
Moshav Zekenim: This is difficult, for it says (Kidushin 30b) that a father and son engaging in Torah become enemies, i.e. they do not disagree respectfully! This is only when they engage together. At other times, one may not disagree (like an enemy).
Why does it say "Es Avicha v'Es Imecha"?
Kesuvos 103a: These include the father's wife, the mother's husband, and [from the Vov in v'Es] one's older brother.
In Bava Kama (54b), R. Chanina ben Agil asked why was "good" in the second Luchos, but not in the first, and R. Chiya bar Aba was unsure whether 'good' was said. Did he not know the verse?! And the Gemara concludes that it is lest 'good' cease from Yisrael, for the first Luchos would be broken. Why is there no concern lest "Ya'arichun Yamecha (your days will be lengthened)" cease?
Divrei Eliyahu: He asked why the first Luchos did not allude to this world. Ya'arichun Yamecha refers to the world to come, and "Yitav Lach", which is only in the second, refers to this world. R. Chiya was unsure whether there is any promise of this world in the Torah, like R. Yakov, who expounds (Kidushin 39b) everything for the world to come. The Tartzan held that Yitav Lach refers to this world. Had it been in the first Luchos, no good would remain in this world. However, length of days remains for the world to come. The letters flew off the Luchos, but they remained in their place above.
In Sanhedrin (88b), the Gemara asked that perhaps one is liable only for cursing both parents together. Why did it not ask if Kivud Av v'Em applies only when they are together?
Perhaps it is because we include from "Es Avicha v'Es Imecha" the father's wife and the the mother's husband (Kesuvos 103a). It is unreasonable to say that the Mitzvah applies only to all of these together (i.e. both parents remarried