Dictionary entry

σκληρύνω

G. Abbott-Smith's A Manual Greek Lexicon of the New Testament

σκληρύνω

(< σκληρός), [in LXX chiefly for קשׁה hi., also for חזק;]

to harden. Metaph., to harden, make stubborn: c. acc. pers., Ro 9:18; τ. καρδίας (Ps 94 (95):8), He 3:8, 154:7. Pass., to become hardened: Ac 19:9, He 3:13.†