The Spirit and the water and the blood (to pneuma kai to udwr kai to aima). The same three witnesses of verses John 67 repeated with the Spirit first. The three (oi trei). The resumptive article. Agree in one (ei to en eisin). "Are for the one thing," to bring us to faith in Jesus as the Incarnate Son of God, the very purpose for which John wrote his Gospel ( 20:31 ).