Albert Barnes Commentary Psalms 31:4

"Pluck me out of the net that they have laid privily for me; For thou art my stronghold." — Psalms 31:4 (ASV)

Pull me out of the net - See the notes at (Psalms 9:15).

That they have laid privily for me - That my enemies have laid for me. The phrase “laid privily” refers to the custom of “hiding” or “concealing” a net or trap, so that the wild animal that was to be caught could not see it, or would fall into it unexpectedly. Thus, his enemies designed to overcome him, by springing a net upon him at a moment when he was not aware of it, and at a place where he did not suspect it.

For thou art my strength - My stronghold. My hope of defense is in you, and you alone.