30 and their sight was restored. Jesus warned them sternly, “See that no one knows about this.”

Read Matthew 9:30 Using Other Translations

And their eyes were opened; and Jesus straitly charged them, saying,See that no man know it.
And their eyes were opened. And Jesus sternly warned them, "See that no one knows about it."
Then their eyes were opened, and they could see! Jesus sternly warned them, “Don’t tell anyone about this.”