And he that hath seen hath borne witness, and his witness is true: and he knoweth that he saith true, that ye also may believe.

The one who saw it has testified to this, and his testimony is true. He knows that he is telling the truth, so that you also may believe.

and he who hath seen hath testified, and his testimony is true, and that one hath known that true things he speaketh, that ye also may believe.

And he who saw it bears witness, and his witness is true, and he knows that he says true that ye also may believe.