σκληρ-ύνω · sklēr-ynō — LSJ
harden, opp. μαλάσσω, Hp. Acut. 45, Arist. HA 548b23:—Pass., with pf. ἐσκλήρυσμαι Hp. Liqu. 6, and -υμμαι, to be hardened, grow hard, Id. VM 22, Thphr. Lap. 11.
metaph., σ. τὴν καρδίαν τινός harden his heart, LXX Ex. 7.3, al., Ep.Hebr. 3.8, cf. Ep.Rom. 9.18:—Pass., LXX Si. 30.12.