What do we learn from "ba'Boker Zera Es Zar'echa vela'Erev Al Tanach Yadecha"?
Rashi citing Yevamos 62b #1: If one learned Torah in his youth, he should learn in his old age. If he had Talmidim in his youth, he should have Talmidim in his old age. (Refer to 11:6:2:1.)
Rashi, from Yevamos 62b #2: If one married a fertile woman in his youth, he should marry a fertile woman in his old age. If he had children in his youth, he should have children in his old age. (Refer to 11:6:2:1.)
Rashi: If you did Tzedakah in your youth, do Tzedakah in your old age.
Ibn Ezra: "Ba'Boker" means constantly. "Tanach" is feminine, for the subject is "Yadecha." We do not find that Hani'ach is Po'el Yotzei Shelishi 1 .
Rashbam: Do not cease your work in your old age. Toil in your work as much as you can.
Rid: If you seeded in Bechir (the early time to seed), seed also in Lakish (the late time to seed).
Seforno: Strive to father children in your youth, and do not cease in your old age, even if you fathered in your youth.
Metzudas David: Constantly seed you field. Do not wait for wind.
I.e. one causes a second to act on a third party. Therefore, the verse does not tell you not to make your hand abandon the seed. (PF)
Why does it say "Ki Einecha Yode'a Ei Zeh Yichshar ha'Zeh Oh Zeh v'Im Sheneihem k'Echad Tovim"?
Rashi, from Yevamos 62b: You do not know if your Talmidim and children of youth will endure for you, or those of your old age. R. Akiva had 24,000 Talmidim. They all died. The world was desolate until he went and taught R. Meir, R. Yehudah, R. Yosi, R. Shimon and R. Elazar ben Shamu'a. They stood up the Torah at that time. Rashi - regarding children, Avtzan (Bo'az) married off 30 daughters and 30 sons, and all of them died in his lifetime. In his old age he fathered Oved (from Rus), and he survived.
Rashbam: You do not know which time is good to seed.
Seforno: Due to one child who will be proper, it is proper to strive to attain it in your youth and in your old age.
Metzudas David, Metzudas Tziyon: You cannot know which seeding will be proper and good.