'Rashi': We do not have a portion and inheritance in the land, only [permission] to live in it. This is like "Ki Gerim v'Soshavim Atem Imadi" (Vayikra 25:23).

Malbim: We cannot acquire here in the land, since we are Gerim here, just like a stranger from another land who is not a native. We are not residents from of old. Rather, we were born recently, and the Nefesh in us, its source is from another world.

'Rashi': If a man has sons and inheritances, and he sold them, and his sons come to live in what he sold, they are called Gerim and Toshavim. However, our fathers were guests. David said, we are not so. Also we and our fathers, all of us are Gerim and Toshavim in the world - "Lecha Shamayim Af Lecha Aretz Tevel u'Melo'ah Atah Yesadtam" (Tehilim 89:12).

Radak: We are not like Toshavim (settlers) in this world, rather, like our fathers, who died. If so, we are Gerim!

Malbim: Also when we are Toshavim (settlers) here, we are like our fathers, who were here for a limited time, and traveled from here.

'Rashi' citing Midrash Koheles 1:2: It is not like the Tzel (shade) of a tree, which is for years, nor like Tzel of a flying bird, for a short time - rather, like shade of a bee's wings. It has wings, but no shade (its wings are transparent)!

Radak: Just like a shadow passes quickly, also our days on the land.

Malbim: Just like a shadow, the longer it gets, this is a sign that soon [the sun will set], and it will go away, likewise, the longer we live, the closer we are to death.

'Rashi': There is no one who has hope not to die.

Radak: There is no hope that a man will live long ¹ , for our days are determined. Malbim - therefore, our acquisitions here are temporary, and are not truly ours.