The gospel of John repeatedly refers to Jesus as the light of the world. It says John the Baptist was sent to testify about “the light of all mankind” that was coming into the world. One of the ways it describes God sending his son into the world is by saying that light has come into the world. And most importantly, it has Jesus call himself the light of the world.
In the gospel of Matthew, though, Jesus tells his disciples that they’re the light of the world.
(Even in John, there’s one passage where Jesus mentions “this world’s light” and doesn’t seem to be talking about himself, since it doesn’t sound like this light was always present when Jesus was in Judea.)