All my bones shall say, Lord, who is like unto thee? The "bones" here represent, not the frame only, as in Psalms 34:20, but the entire nature. David promises that his whole nature shall bear witness to God's mercy and goodness, proclaiming that there is "none like unto him" in these respects, none other that can deliver from danger as he can and does.
As Hengstenberg observes, "He seeks to make the Lord grant the desired help by promising that the help afforded would yield a rich harvest of praise and thanksgiving." Which deliverest the poor from him that is too strong for him, yea, the poor and the needy from him that spoileth him?
(comp. Psalms 86:1, where David again calls himself "poor and needy;" i.e. in want of help and peace and comfort; not absolutely without means, or he would not offer any temptation to the spoiler.