This verse describes God as the One who rescues. It explains or is the reason for the praise in Psalm 144:9. That is why we may start this verse with the word for.
Literally, our verse says that God is rescuing kings, saving his servant David from the evil (murdering) sword.
Kings owe their victory and redemption to God and the same goes for David—even from the time that he conquered Goliath. There are translations that connect the end of Psalm 144:10 to Psalm 144:11, so that it reads: rescue me from the murdering sword.
We do not support that, because at the end of Psalm 144:10 we think of how the Lord supported David in his battle against Goliath.
10 who gives victory to kings, who rescues David his servant from the cruel sword.