Jamieson, Fausset and Brown on John 4:39-42

39-42. many ... believed, &c.--The truth of Joh 4:35 begins to appear. These Samaritans were the foundation of the Church afterwards built up there. No miracle appears to have been wrought there (but unparalleled supernatural knowledge displayed): "we have heard Him ourselves" (Joh 4:42) sufficed to raise their faith to a point never attained by the Jews, and hardly as yet by the disciples--that He was "the Saviour of the world" [Alford]. "This incident is further remarkable as a rare instance of the Lord's ministry producing an awakening on a large scale" [Olshausen].