The Greek word marturion means testimony, proof, or public witness. It is closely related to marturia (G3141) but often emphasizes the objective evidence or proof offered as testimony, especially in a public or formal setting. In the Synoptics it frequently appears in the phrase 'as a testimony to them' — miraculous healings and proclamation serving as evidence that demands a verdict.
Jesus consistently sends healed people to show themselves to the priests 'as a testimony (marturion) to them' — the miracle is not merely an act of compassion but a piece of evidence in the ongoing trial of who Jesus is. Matthew 24:14 promises that 'this gospel of the kingdom will be preached in the whole world as a testimony (marturion) to all nations.' The Great Commission is fundamentally a witness-bearing enterprise — the church exists to present the evidence of Christ's resurrection and redemption before the court of history. The tabernacle was called the 'tent of testimony' in the LXX — God's dwelling among His people being itself a witness to His nature.