Bebaioō (βεβαιόω) means to confirm, establish, make sure or firm. From the adjective bebaios (firm, steadfast), it conveys the idea of ratifying, validating, or making something reliable. In the New Testament it describes God's confirmation of the gospel (Mark 16:20), the establishment of believers in Christ (1 Corinthians 1:6–8; Colossians 2:7), and the ratification of a covenant (Romans 15:8).
The word bebaioō captures the divine guarantee behind the gospel. When God confirms the word with signs (Mark 16:20), when Christ confirms the promises (Romans 15:8), when the Spirit's gifts confirm believers (1 Corinthians 1:6), the eternal God is staking His character on the truth of His promises. Hebrews 2:3 uses this word to describe how the great salvation was "confirmed to us by those who heard." The believer's security rests not on human performance but on God's confirming faithfulness.