A zeal for God (zhlon qeou). Objective genitive like Philippians 3:9 , "through faith in Christ" (dia pistew Cristou). But not according to knowledge (all ou kat epignwsin). They had knowledge of God and so were superior to the Gentiles in privilege ( Philippians 2:9-11 ), but they sought God in an external way by rules and rites and missed him ( Philippians 9:30-33 ). They became zealous for the letter and the form instead of for God himself.