Jamieson, Fausset & Brown

Then went this saying abroad among the brethren, that that disciple should not die--into which they the more easily fell from the prevalent expectation that Christ's second coming was then near at hand. yet Jesus said not unto him, He shall not die--The Evangelist is jealous for His Master's honor, which his death might be thought to compromise if such a misunderstanding should not be corrected.