What do we learn from "Re'eh Chayim Im Ishah"?
R. Avigdor, from Kidushin 30b: One must teach a trade to his son. "Ishah" literally means a wife, or, it alludes to Torah. In either case, just like it is a Mitzvah to take a wife for one's son or to teach to him Torah, it is also a Mitzvah to teach to him a livelihood.
Rashi: See and understand to learn a trade for income, together with Ishah (Talmud Torah).
Ibn Ezra (8): Marry a woman, and do not stumble with a foreign woman.
Rashbam: Rejoice in your portion with your wife.
Seforno: Chayim is real life, i.e. eternal life - "u'Vacharta ba'Chayim" (Devarim 30:19). "Im Ishah" is with temporary pleasure.
Metzudas David #1: See that your life is life, that you will have pleasure. Life of pain is not called life. You should have pleasure, and also the wife that you took, she should not be stingy towards you. Therefore, have pleasure with her all the days that Hashem allotted to you to live in this world.
Metzudas David #2: Dwell with your wife in Shalom, so you will have life. Life of quarrels is not called life.
What is "Yemei Hevlecha"?
Seforno: The days of youth, which are Yemei Chayim, the opposite of old age, which is called the days of old age, which are called "Yemei ha'Ra'ah" (12:1). This is like "u'Zechor Es Bore'echa bi'Ymei Bechurosecha" (ibid.) I told you to see and choose life in Yemei Hevlecha. This sight and choice Hashem gave to you your entire life, not after death. Yemei Hevlecha are short, and the task is great. The attained purpose is a high level - "Ki Tov Yom b'Chatzerecha me'Alef" (Tehilim 84:11) - one moment of Torah and good deeds in this world is better than all life of the world to come (Avos 2:21).
Metzudas David: Your days in this world are called Hevel, because they are not eternal.
Why does it say "Ki Hu Chelkecha ba'Chayim"?
Rashi: If you do so, your portion will be life in this world to be financed via the trade, and in the world to come, for exertion of both of them - Torah and Derech Eretz - makes sin forgotten (non-existent) (Avos 2:2).
Rashbam: This is the only thing that Hashem gave to you - to eat bread, wear clothing, and marry a woman and rejoice in her.
Seforno: Only this is your [exclusive] portion - everything else, also strangers have with you.
What do we learn from "uva'Amalecha Asher Atah Amel Tachas ha'Shamesh"?
Ri Kara: This refers to "Lech Echol b'Simchah Lachmecha" (7). Also rejoice in your toil Tachas ha'Shamesh in this world.
