He came as a witness, to testify about the Light, so that all might believe through him.
The same came for a witness, to bear witness of the Light, that all men through him might believe.
This man came to witness, that he might testify of the Light, that all men might believe in it [adhere to it, trust it, and rely upon it] through him.
The same came for witness, that he might bear witness of the light, that all might believe through him.
He came as a witness to testify concerning the light, so that through him everyone would believe in the light.
He arrived as a witness to offer testimony about the Light, so that all would believe through him.
