What does John 11:26 mean?

In the prior verse, Jesus once again referred to Himself using the "I AM" terminology. This echoes the statement made by God in Exodus 3:14. When Moses asked God to identify Himself, the response was an expression of God's necessary, absolute, perfect existence. God "just is." Jesus' words in the prior verse tie that idea to a very personal concept of salvation. Rather than making mankind's redemption a matter of learning or effort, God grounds our hope in a person: "the light of the knowledge of the glory of God in the face of Jesus Christ" (2 Corinthians 4:6).

Jesus expands that idea with a wordplay on the ideas of life and death. Jesus' other teachings emphasize the concept of "eternal life" (John 3:16; 5:24; 10:28). Those who place their faith in Christ have a life which cannot be taken away (John 10:29), and which exists beyond the death of the physical body (2 Corinthians 5:1–5). The Greek phrase Jesus uses here is exactly the same as in John 10:28, and means something which will "never, ever" occur.

Jesus is speaking to Martha, one of Lazarus' sisters (John 11:1–3). His question to her uses a verb—an expression of action—rather than a noun. The term translated as "believe" here is from the Greek root word pisteuo, referring to "faith." Prior comments by Martha show that she's willing to put trust in Jesus (John 11:22), likely based on having heard His message in the past (Luke 10:38–42). When asked if she has faith in Christ and His promise of resurrection, she responds with a clear statement of Jesus' status as God and Messiah (John 11:27).