Shocher Tov (54): I should not descend to Gehinom. If You will not be a guarantor for me, who can be?!

Rashi: This is an expression of salvation. Be a guarantor for me against evil (that I will guard Your Pikudim).

Radak: This is like "v'Arvah la'Shem" (Mal'achi 3:4), "v'Arvah Shenasecha" (Mishlei 3:24) (will be pleasant). However, this is Po'el Yotzei (it acts on others) - make Your servant good and proper for [receiving] good, "that Zedim will not oppress me."

Malbim: This is a metaphor, as if the good prepared for him, he requests Hashem to be a guarantor that it not fall to strangers via oppression. Rather, it will remain in his hand. Then, he can request is from Him, and He must return it, for he accepted Arvus!