What are the implications of the words "Vehechezakta bo"?
Rashi: It means that one should support him, to prevent him from falling any further. 1
Rashi: This can be compared to a load on a donkey; as long as it is still on the donkey's back, one person can grab hold of it and support it. However once it has fallen to the ground, even five people cannot prop it up.
Whom exactly is one obligated to support?
What is the meaning of "Ger ve'Toshav"?
Rashi: "Ger" refers to a Ger Tzedek; "Toshav", to a Nochri who has undertaken not to worship idols, even though he eats Neveilos. 1
Targum Onkelos and Targum Yonasan: Both refer to Nochrim who are strangers, 2 though the difference between then is unclear.
What are the ramifications of the phrase "va'Chai Imach"?
Ramban #1: Based on the implication from the word "Imach" - that your life takes precedence over that of your fellow-Jew - it teaches us the Mitzvah of self-preservation. 1
Ramban #2 (citing Targum Onkelos) and Targum Yonasan: It is a Mitzvah to sustain the stranger and the Toshav.
Ramban (citing the Toras Kohanim): As R. Akiva countered ben Putiri (who, in the case of Reuven and Shimon who were traveling in the desert, based on the Pasuk "va'Chei Achicha Imach", and Reuven had sufficient water for one person, ruled that they should share it) and, based on the same Pasuk, ruled that Reuven's own life takes precedence over Shimon's. The Ramban is referring basically to this Pasuk (and "ve'Chai Achicha Imach" is a repetition that comes to emphasize the issue (See R. Chavel's footnotes).