"Yahweh will be by your side." A person standing by another person's side is an idiom that means that the one person will help and support the other. AT: "Yahweh will support and defend you" (See: [[rc://en/ta/man/translate/figs-idiom]])
The writer speaks of a person experiencing harm from "terror" and "devastation" as if the person were caught in a trap. The word "foot" represents the whole person. AT: "will protect you from those who want to harm you" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-synecdoche]])