Oh give us help against the adversary, For deliverance by man is in vain.
A couple of things hit me from the last phrase of this verse. First, deliverance is possible by man, but second, deliverance by man is worthless.
Many times we will look for help and deliverance from man and maybe even feel we have found it. The army of Israel could fight and possibly win the battles against their enemy, but David understood that if they did not do it through God and with His help it was all in vain. God is our deliverer and our help. Only with Him and through Him do we find true deliverance that matters.
Too many times we have our deliverance defined and we work for it in our own strength. But we should look to God's deliverance to walk through any challenge with Him. We might find deliverance in our definition, and people might call that a victory. But if it is through our own strength it is worthless and in vain.
Lesson: I would rather walk through challenging circumstances with God than share in victories by man