Psalm 35:10 (ESV) …. All my bones shall say, “O Lord, who is like you, delivering the poor from him who is too strong for him, the poor and needy from him who robs him?”
He wanted what we call fair play. We get a great deal of satisfaction, for instance, in seeing a bully meet his match.
Richard Llewellyn illustrates that in How Green Was My Valley. Young Huw had been sent to the school on the other side of the mountain. The schoolmaster took an instant dislike to his new pupil. He bullied him, held him up to ridicule, and finally thrashed him to within an inch of his life. Young Huw dragged himself home. Two of his older brothers, tough young colliers, their muscles hardened in the coal mines, decided to teach the bully a lesson he would never forget. Over the mountain they went and into the school. Having dealt with others who tried to intervene, Huw’s brother Dai seized the schoolmaster around the neck, bent him over his knee, took off his belt, and gave him the thrashing of his life. When he had finished, the young coal miner pitched the wretched schoolmaster head over heels through the open trap of the coal cellar and shut the lid. Young Huw never had to fear that schoolmaster again.
Our very bones, as David puts it, thrill within us when we see justice being done and the fearful injustices of life being corrected. That is what David wanted done to his fears!
Now comes a change of pace. We have been looking at David in the camp, appealing to the Lord as a warrior. There were foes he could not fight, foes too sly for him, so he turns them over to the Lord.[1]
[1] Phillips, J. (2009). Exploring Psalms 1–88: An Expository Commentary (Vol. 1, Ps 35:10). Kregel Publications; WORDsearch Corp.