Asar means to bind, tie, imprison, or harness. It is used in a wide range of contexts: binding prisoners, harnessing horses to chariots, binding vows or oaths, and the chains of captivity. The related noun asir means prisoner or captive.
The verb asar carries both physical and spiritual dimensions in Scripture. God's people were bound in chains in Egypt and Babylon, but the great theme of Scripture is liberation from bondage. Jesus came to set the captives free (Luke 4:18). Conversely, the binding of vows (neder) reflects the sacred seriousness of promises made before God — words that bind.