σκληρύνω

I harden

Definition

The verb σκληρύνω means 'to harden' or 'to make hard,' primarily in a metaphorical sense of causing someone to become stubborn, unyielding, or resistant. In the New Testament, it most often describes a spiritual or moral hardening of the heart against God's will or message. For example, in Romans 9:18, it is used of God's sovereign action in hardening Pharaoh's heart, echoing the Exodus narrative. In Hebrews 3:8, 13, 15, and 4:7, it warns believers not to harden their hearts as Israel did in the wilderness, emphasizing a willful resistance that leads to unbelief.

Biblical Usage

This word is used six times in the New Testament, appearing in Acts, Romans, and Hebrews. In Acts 19:9, it describes some Jews becoming obstinate and refusing to believe Paul's message in the synagogue. In Romans 9:18, it references God's sovereign role in hardening. The four occurrences in Hebrews (3:8, 3:13, 3:15, 4:7) all quote Psalm 95:7-8, creating a repeated exhortation for the Christian community to avoid the pattern of rebellious unbelief shown by Israel.

Etymology

Derived from the Greek adjective σκληρός (sklēros, G4642), meaning 'hard,' 'harsh,' or 'difficult.' The verb form σκληρύνω literally means 'to make hard.' This root gives us the English medical term 'sclerosis,' referring to a hardening of tissue. The word's meaning evolved from a physical sense to a metaphorical one describing stubbornness of will or spirit.

Semantic Range

This word is theologically significant as it touches on the complex interplay between divine sovereignty and human responsibility. In Romans 9:18, it is used in the context of God's elective purpose, while in Hebrews, it is a urgent warning to believers about their own responsibility to respond to God's voice. Understanding this Greek term enriches reading by highlighting that a 'hardened heart' is not mere ignorance but an active, culpable resistance to divine revelation, with serious spiritual consequences.

In the ancient Greco-Roman and Jewish world, the 'heart' (καρδία) was considered the center of intellect, will, and moral character. To 'harden' the heart was not about emotions becoming cold, but about the will becoming fixed in rebellion or disobedience. The biblical usage, especially in Hebrews' quotation of Psalm 95, directly recalls the foundational story of Israel's testing in the wilderness, a cultural touchstone for failure and unbelief.

πωρόω (pōroō, G4456) — to harden, often with a sense of making dull or insensitive; ἀπείθεια (apeitheia, G543) — disobedience, the resulting state of a hardened heart.

Word Details

Scripture References