It’s interesting that in Codex Vaticanus, there is a “correction” to the original text and then a marginal note on Hebrews 1:3.

The original and correct Greek version of Hebrews 1:3 read:

“He reflects the glory of God and bears the very stamp of his nature, UPHOLDING (φερων) the universe by his word of power. When he had made purification for sins, he sat down at the right hand of the Majesty on high.”

But the manuscript was changed by someone to read:

“He reflects the glory of God and bears the very stamp of his nature, REVEALING (φανερων) the universe by his word of power. When he had made purification for sins, he sat down at the right hand of the Majesty on high.”

A marginal note reads: “Fool and knave, leave the old reading and do not change it!”

What does this mean?

1. We know that early biblical scribes changed the text either on purpose or by accident.
2. My guess here is that somebody with proto-Arian tendencies did not like the idea of the Son of God “upholding the universe.” That, he thought, is the job of God the Father! So he changed a few letters for it read “revealing the universe.”
3. Another explanation is that these manuscripts were created by one man reading the text aloud and another man writing it down. So he heard the word wrongly and changed a few letters on accident.
4. We also see that Christians would feel free to write corrections or even rebukes in the margins of NT texts.