What is the meaning of "Es'halech Lifnei Hashem"?
Radak (citing Pesachim 118a): I will go in front of Tzadikim at Techiyas ha'Mesim.
Malbim: Tzadikim go in front of Hashem - "His'halech Lefanai ve'Hye Samim" (Bereishis 17:1).
What are "Artzos ha'Chayim"?
Rashi: It is Eretz Yisrael. My enemies and pursuers expelled me from it in the days of Sha'ul, and Bal Korcham (against their will) I returned. Radak - it is Eretz Yisrael and the cities of Yisrael. It is called also "Eretz Tzvi" (Yechezkel 25:9) and "Eretz Chefetz" (Mal'achi 3:12). David said this when he was among the Pelishtim.
Radak: This is the converse of "Chilatzta Nafshi mi'Maves" (8).
Radak (citing Pesachim 118a): This refers to Techiyas ha'Mesim.
QUESTIONS ON RASHI
Rashi writes that "Artzos ha'Chayim" is Eretz Yisrael. Why is it called so?
Radak #1: His Shechinah is there.
Radak #2: Chayim refers to health - "Ad Chayosam" (Yehoshua 5:8). The air of Eretz Yisrael is better than that of all lands - "Yefe Nof Mesos Kol ha'Aretz" (above, 48:3), "u'Val Yomar Shachen Chalisi" (Yeshayah 33:24) - one who dwells in Yerushalayim will not say 'I fell ill.'
Radak citing Yerushalmi Kil'ayim 9:3: Its dead live at Techiyas ha'Mesim 1 .
Our text says 'its dead live first in the days of Mashi'ach.' (Radak's text is difficult. All Yisrael have a share in the world to come! - PF)