Jesus said, “If those who lead you say, ‘See, the Kingdom is in the sky,’ then the birds of the sky will precede you. If they say to you, ‘It is in the sea,’ then the fish will precede you. Rather, the Kingdom is inside of you, and it is outside of you. When you come to know yourselves, then you will become known, and you will realize that it is you who are the sons of the living Father. But if you will not know yourselves, you dwell in poverty and it is you who are that poverty.”
This is an exert from The Gospel According to Thomas or what has become to be known as The Gospel of Thomas. This gospel is considered non-canonical. Per Wikipedia:
It was discovered near Nag Hammadi, Egypt, in December 1945, in one of a group of books known as the Nag Hammadi library. The Gospel of Thomas was found among a collection of fifty-two writings that included, in addition to an excerpt from Plato’s Republic, gospels claiming to have been written by Jesus’s disciple Philip. Scholars have speculated that the works were buried in response to a letter from Bishop Athanasius who for the first time declared a strict canon of Christian scripture.
You can read more about this gospel here.
The introduction states: “These are the hidden words that the living Jesus spoke and Didymos Judas Thomas wrote them down.” However, some critical scholars believe the reference to Thomas is false and the true author is unknown.
Regardless of the controversy, the words are beautiful and powerful and echoed by other prophets and sages across the ages.