What is the meaning of "Ki Yipol"?
Rashi: If he will slip. This is like "va'Tipol me'Al ha'Gamal" (Bereishis 24:64).
Radak: If a Tzadik will fall, and lose his property.
Malbim: If he will fall - physically, or from his level or success.
What is the meaning of "Lo Yutal"?
Rashi: He will not be abandoned.
Radak: He will not be cast on the ground.
Why does Hashem support him only after he fell, and not prevent him from falling?
Radak: The affliction was due to Musar and love - "Ki Es Asher Ye'ehav Hashem Yochi'ach" (Mishlei 3:12). This is unlike a Rasha - when he falls, he is cut off and does not rise; however, "Ki Sheva Yipol Tzadik v'Kam" (ibid., 24:16).
Malbim: Falling was for his good. Hashem saw that the path [on which he wanted to go] was bad for him; his body or Nefesh would be damaged. Hashem sent an obstacle to stop him.
