Rashi: Your guarantor. R. Yonah - because Tzadikim are saved from sin, and trust in Hashem, He will do a miracle for them and save them, even if the place will be destroyed.

Rashi (citing Yerushalmi Pe'ah 1:1): [Your guardian] in matters in which you are a Kesil (fool).

Malbim: Kasel is Bitachon that evil will not occur to him. He does not do any act to save from evil; he relies on Hashem and does not fear.

R. Yonah: He will guard you from being caught in sin. This is like "Avonosav Yilkeduno Es ha'Rasha" (5:22), "Yakoshti Lach v'Gam Nilkadt" (Yirmeyah 50:24). With guarding the Torah and Bitachon, Hashem shields one who hopes to Him, from every affliction - "Imras Hashem Tzerufah Magen Hu l'Chol ha'Chosim Bo" (Tehilim 18:31). Also Shlomo said so ¹ . Alternatively, "l'Chol ha'Chosim Bo" are those who do not question the reason for His sayings.

Malbim: Even though at the time of affliction, one who does not think [how] to be saved can easily be caught in a trap, since your hope is in Hashgachas Hashem, He will guard your feet from being caught in it.