What does Psalm 7:10 mean?

A warrior uses his shield to defend himself from attack. In the same way, David believes God defends him against his enemies. The phrase "with God" implies that David is entrusting his defense entirely to the Lord. There may be a physical aspect to this prayer of protection (1 Samuel 24:1–2), but it may also be about slander and lies (Psalm 7:1; 3–5). David is confident that God is the ultimate, righteous Judge (Psalm 7:6–9). David knows he is innocent of those crimes, so he has reason to believe the Lord will vindicate him.

God's deliverance is not always as soon as we would prefer (Habakkuk 1:2–4), but it is always complete. He delivered the Israelites at the Red Sea from the approaching Egyptian cavalry (Exodus 14). The Lord parted the waters so the Israelites could cross safely, but closed them when the Egyptians entered, drowning their army. In the time of Daniel, God delivered Daniel's three friends from a furnace that was heated seven times beyond its normal temperature, and the three men emerged unharmed without even the smell of smoke on them (Daniel 3:19–27). The Lord also delivered Daniel from a den of hungry lions (Daniel 6:19–23).

The Lord defends His people today, as well. Nothing happens without our Lord's permission. As difficult as those experiences may be, they are meant for our good and His glory (John 16:33; Romans 8:18–39).