"Jesus said, "I disclose my mysteries to those [who are worthy] of [my] mysteries."
http://www.gnosis.org/naghamm/gosthom.html
"Jesus told his disciples that he spoke in parables so that no one else would understand what he was saying. (His teaching was a secret that he shared only with his disciples.)"
https://skepticsannotatedbible.com/contra/secret.html
"The Gnostic Christians claimed to possess the correct definition of "resurrection" - based on Jesus' secret teachings, handed down to them by the apostles."
https://reluctant-messenger.com/Lost-Doctrines-Christianity003.htm
"Secret teachings of Jesus or his disciples which were passed down privately. In most cases these teachings would initially be transmitted through private conversations, but eventually someone would write them down, often in the form of secret sayings."
https://gospel-mysteries.net/secret-gospels.html
"An ancient Christian tomb was discovered in 1945 when workers in Egypt found 13 leather-bound manuscripts, which revealed more information about the sect of Christians called “Gnostics,” meaning they teach salvation through mystical knowledge.
This sect was ultimately destroyed by the Roman orthodox church. Their followers were burned at the stake and their writings were destroyed."
https://garylite.com/2018/08/28/the-lost-forbidden-teachings-of-jesus/
"10And he said, Unto you it is given to know the mysteries of the kingdom of God: but to others in parables; that seeing they might not see, and hearing they might not understand."
https://biblehub.com/kjv/luke/8.htm