Not the hearers - but the doers (ou gar hoi akroatai̇̇all' hoi poiētai). The law was read in the synagogue, but there was no actual virtue in listening. The virtue is in doing. See a like contrast by James between “hearers” and “doers” of the gospel (Jam 1:22-25).
Before God (para tōi theōi). By God’s side, as God looks at it.
Shall be justified (dikaiōthēsontai). Future passive indicative of dikaioō, to declare righteous, to set right. “Shall be declared righteous.” Like Jam 1:22-25.