Extended Strong's Greek Lexicon (Abbott-Smith based)
hardness of heart
Usage: σκληρο-καρδία, -ας, ἡ (σκληρός, καρδία), [in LXX: Deu.10:16, Jer.4:4 (לֵבָב עׇרְלָה), Sir.16:10 (cf. καρδία σκληρά, Sir.3:26-27) * ;] hardness of heart: Mat.19:8, Mrk.10:5 16:14.† (AS)