This passage is initially about priests and the sacrificial system, but is also about hope and hopelessness, and about rescue. Paul reminds his readers that unlike Jesus, the Old Testament priests offered sacrifices over and over again but, as the paraphrase The Message puts it, "it never makes a dent in the sin problem" (10:11). That makes us hapless prisoners of sin.
My family and I were recently looking into a fishpond. Below the surface, quietly waiting for bits of food the other fish dropped, was a Jewfish (yes, that's his real name. He is a type of Grouper). Being a grouper this fish is good to eat, but being a Jewfish, he is protected by law (because of his gamefish status, not his religion). This is how he (or she) came to be in the fishpond; his life was about to end in the bottom of a fisherman's cooler. He was found by the police in the nick of time and the fisherman was apprehended. The Jewfish was revived and now lives in the fishpond.
As I watched him there in his pond, my heart went out to him. He was cute, in a lumpy, splotchy black and orange kind of way. I felt bad that he was once a hapless prisoner.
That sort of gut reaction, multiplied many times over, is how Scripture says God looked down on us, and caused Him to have mercy on us and to send His son, so that once for all, we would be free of the sin problem. (Hebrews 10:12). It was a rescue effected for some hapless prisoners of sin, and I pray that God continues to make us thankful for His mercy.