In Isaiah 41:14 ESV it says “Fear not, you worm Jacob, you men of Israel! I am the one who helps you, declares the LORD; your Redeemer is the Holy One of Israel.”

StudyLight.org Adam Clarke’s commentary:

“Fear not, thou worm Jacob – In the rabbinical commentary on the five books of Moses, Yelamedenu, it is asked, Why are the Israelites called a worm? To signify, that as the worm does not smite, that is, gnaw the cedars, but with its mouth, which is very tender, yet it nevertheless destroys the hard wood; so all the strength of the Israelites is in prayer, by which they smite the wicked of this world, though strong like the cedars, to which they are compared, Ezekiel 31:3.”

This site also has a good explanation: https://gracevalley.org/sermon/the-theology-of-a-worm/