1)
What is the significance of "Yisha'en Al Beiso v'Lo Ya'amod"?
1.
Devar Eliyahu: One who relies on his wealth, it will not stand for him - "Lo Yo'il Hon b'Yom Evrah."
2.
Devar Eliyahu (17): This refers to his children, who are called 'a support [for my old age' - Kesuvos 64a].
3.
Malbim: If a Rasha is uprooted from his place, he will not flourish elsewhere, like a reed or grass. Further, even if he remains in his house, it will not stand. Tzadikim are like a tree, which can be uprooted and replanted elsewhere.
2)
Why does it add "Yachazik Bo v'Lo Yakum"?
1.
Devar Eliyahu: He does not want to leave his house in any circumstance. He wants to be fixed there forever. This will not be fulfilled.
