King James Bible
"The same came for a witness, to bear witness of the Light, that all men through him might believe."
This refers to John the Baptist, introduced in the previous verse, whose divinely appointed purpose was to testify. The repetition of 'witness' emphasizes that John's entire mission centered on pointing beyond himself to validate another's identity. The Light is Christ, introduced metaphorically in verse 4-5 as the source of spiritual illumination for humanity. John's testimony serves to identify and authenticate Jesus as this divine Light entering the darkness of the world. The ultimate goal extends universally—John's witness aims to bring all people to faith in Christ. The phrase 'through him' clarifies that John serves as the instrumental means, not the object of belief, functioning as a bridge between humanity and the Light.