How can it be a later development by other people when Jesus supposedly directly said it? https://www.kingjamesbibleonline.org/Matthew-19-23/
Then said Jesus unto his disciples, Verily I say unto you, That a rich man shall hardly enter into the kingdom of heaven. And again I say unto you, It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God.