“And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth (John 1:14 KJV).”
It wasn’t hearsay.
Simeon saw salvation.
“And, behold, there was a man in Jerusalem, whose name was Simeon; and the same man was just and devout, waiting for the consolation of Israel: and the Holy Ghost was upon him.
And it was revealed unto him by the Holy Ghost, that he should not see death, before he had seen the Lord’s Christ.
And he came by the Spirit into the temple: and when the parents brought in the child Jesus, to do for him after the custom of the law,
Then took he him up in his arms, and blessed God, and said,
Lord, now lettest thou thy servant depart in peace, according to thy word:
For mine eyes have seen thy salvation,
Which thou hast prepared before the face of all people;
A light to lighten the Gentiles, and the glory of thy people Israel (Luke 2:25-32 KJV).”
JESUS is the light.
“Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life (John 8:12 KJV).