The adjective chazaq means "strong," "mighty," "severe," or "hard." It describes physical strength, military power, emotional fortitude, or the intensity of divine action. The related verb (chazaq, H2388) means to be or become strong, to strengthen, to seize, or to repair. Together they form one of the most important word families in the Hebrew Bible.
The call to be chazaq — strong and courageous — runs like a golden thread through the Old Testament. Joshua receives the command "Be strong and courageous" (chazaq ve-ematz) no fewer than four times as he prepares to lead Israel into Canaan (Joshua 1:6,7,9,18). The repeated command reveals an important theological truth: biblical strength is not self-generated but divinely commanded and divinely supplied. We are told to be strong precisely because our strength comes from God, not from ourselves (Philippians 4:13, Ephesians 6:10). The word is also used of God's own "mighty hand" in the Exodus — His irresistible, saving power displayed against Pharaoh.