ACCORDING TO THE THOMAS GOSPEL
39. Jesus said, "The Pharisees and the scholars have taken the keys of knowledge and have hidden them. They have not entered nor have they allowed those who want to enter to do so. As for you, be as sly as snakes and as simple as doves."
The priests (Pharisees) and scholars hide the knowledge of the self and yoga (the keys) that leads to enlightenment (the kingdom of heaven). They do not live according to this knowledge (have not entered, used the keys) and they even stop others from doing so by keeping the knowledge to themselves (do not allow others to enter). You who are entering (as for you), be smart but inconspicuous (sly as snakes) by remaining outwardly humble and peaceful (simple as doves), otherwise they will try to stop you.
40. Jesus said, "A grapevine has been planted apart from the Father. Since it is not strong, it will be pulled up by its root and will perish."
Sometimes, even with good intend, a spiritual path (a grapevine) is created that is planted outside of the truth (apart from the Father). Because it is rooted in error, the error will be found (pulled up by its root) and the path will not last (perish).
65. He said, "A [...] person owned a vineyard and rented it to some farmers, so they could work it and he could collect its crop from them. He sent his slave so the farmers would give him the vineyard's crop. They grabbed him, beat him, and almost killed him, and the slave returned and told his master. His master said, 'Perhaps they didn't know him.' He sent another slave, and the farmers beat that one as well. Then the master sent his son and said, 'Perhaps they'll show my son some respect.' Because the farmers knew that he was the heir to the vineyard, they grabbed him and killed him. Anyone here with two ears had better listen!"
From the Supreme (the owner, the master), a field of spiritual understanding (the vineyard) has been leased to the Pharisees (some farmers) to work with in order to bring about enlightenment (the vineyard's crop). However, when God sends prophets (slaves) to the Pharisees (the farmers) to instruct them to use the knowledge and become enlightened (return the crop), the prophets (slaves) are obstructed (beaten). God then send a truly enlightened being (his son, Jesus), hoping for more respect. Him the Pharisees killed (killed him), because they knew that his understanding by far surpassed theirs (knew that he was the heir to the vineyard) and they feared for their position. They want to possess the knowledge because it gives them power, but they do not want to listen, truly accept it and apply it.
67. Jesus said, "Those who know all, but are lacking in themselves, are utterly lacking."
Those who have a lot of spiritual understanding (know all), but are unable to bring it into true spiritual practice (are lacking in themselves), will be very unhappy (are utterly lacking). Better be ignorant, than to know and ignore the knowledge.
102. Jesus said, "Damn the Pharisees! They are like a dog sleeping in the cattle manger: the dog neither eats nor [lets] the cattle eat."
Jesus damns the scholars and priests (the Pharisees). They guard (like a dog) the understanding of truth (the cattle manger), yet they do not truly study nor follow the truth (neither eat) nor allow other people to do so (nor let the cattle eat).