In "The Progressive Publication of Matthew" page 565 B Ward Powers writes,
[Mark] 10:24 MP: Luke omits entirely Mark's record of the response of the disciples to Jesus's
words: "And the disciples were amazed at his words. But Jesus said to them again,
'Children, how hard it is to enter the kingdom of God!'". Matthew turns "But Jesus said to
them again" into direct speech, "But again I tell you".
[Mark] 10:24 MD: Mark inserts the reaction of the disciples to Jesus's words, and Jesus's
further comments, from his source P.
MP = Markan Priority
MD = Markan Dependency
https://www.sats.edu.za/userfiles/Powers%20DThPOMAL%20Final%20Apr%202010_0.pdf(My [] brackets)
Mark's version:
17And when he was gone forth into the way, there came one running, and kneeled to him, and asked him, Good Master, what shall I do that I may inherit eternal life? 18And Jesus said to him, Why call you me good? there is none good but one, that is, God. 19You know the commandments, Do not commit adultery, Do not kill, Do not steal, Do not bear false witness, Defraud not, Honor your father and mother. 20And he answered and said to him, Master, all these have I observed from my youth. 21Then Jesus beholding him loved him, and said to him, One thing you lack: go your way, sell whatever you have, and give to the poor, and you shall have treasure in heaven: and come, take up the cross, and follow me. 22And he was sad at that saying, and went away grieved: for he had great possessions.
23
And Jesus looked round about, and said to his disciples, How hardly shall they that have riches enter into the kingdom of God! 24And the disciples were astonished at his words. But Jesus answers again, and said to them, Children, how hard is it for them that trust in riches to enter into the kingdom of God! 25It 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. 26And they were astonished out of measure, saying among themselves, Who then can be saved? 27And Jesus looking on them said, With men it is impossible, but not with God: for with God all things are possible.
Matthew's version:
16And, behold, one came and said to him, Good Master, what good thing shall I do, that I may have eternal life? 17And he said to him, Why call you me good? there is none good but one, that is, God: but if you will enter into life, keep the commandments. 18He said to him, Which? Jesus said, You shall do no murder, You shall not commit adultery, You shall not steal, You shall not bear false witness, 19Honor your father and your mother: and, You shall love your neighbor as yourself. 20The young man said to him, All these things have I kept from my youth up: what lack I yet? 21Jesus said to him, If you will be perfect, go and sell that you have, and give to the poor, and you shall have treasure in heaven: and come and follow me. 22But when the young man heard that saying, he went away sorrowful: for he had great possessions.
23Then said Jesus to his disciples, Truly I say to you, That a rich man shall hardly enter into the kingdom of heaven. 24And again I say to 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. 25When his disciples heard it, they were exceedingly amazed, saying, Who then can be saved? 26But Jesus beheld them, and said to them, With men this is impossible; but with God all things are possible.
Luke's version:
18And a certain ruler asked him, saying, Good Master, what shall I do to inherit eternal life? 19And Jesus said to him, Why call you me good? none is good, save one, that is, God. 20You know the commandments, Do not commit adultery, Do not kill, Do not steal, Do not bear false witness, Honor your father and your mother. 21And he said, All these have I kept from my youth up. 22Now when Jesus heard these things, he said to him, Yet lack you one thing: sell all that you have, and distribute to the poor, and you shall have treasure in heaven: and come, follow me. 23And when he heard this, he was very sorrowful: for he was very rich. 24
And when Jesus saw that he was very sorrowful, he said, How hardly shall they that have riches enter into the kingdom of God! 25For it is easier for a camel to go through a needle's eye, than for a rich man to enter into the kingdom of God. 26And they that heard it said, Who then can be saved? 27And he said, The things which are impossible with men are possible with God.
It can be seen from the entire periscope that Matthew and Luke differ 36 times. In 18 of these, Mark agrees with Matthew, and in the other 18, Mark agrees with Luke.
It would be very odd if Matthew and Luke, both using Mark, changed Mark's wording in exactly the places where the other did not. This is what is required by Markan priority. However, with Markan dependence Mark simply conflates Matthew and Luke, at times following one and at times following the other.
Well I think I've got that right. From the above link, page 284:
There are 36 differences of detail most of them of very minor
significance between Matthew and Luke. Their sources were different eyewitnesses:
this explanation accounts for these pericopes in the Majors as they stand. Then Mark
came to these two different accounts, and he melded them marvelously, on 18
occasions choosing to follow Matthew and on the other 18 to follow Luke. (The list of
these 36 differences and how Mark handles them is set out in Chapter Eleven.)
In this we have a simple, clear-cut, straightforward explanation that accounts fully for
what is found in the three Synoptics. But consider the alternatives and what has to be
explained if Mark is first. With this common starting point, Matthew altered his account
from Mark s in 18 ways, small insignificant changes for the most part, and we have to try
and figure out what he was doing and often we simply have to say, He just felt like
changing it. But then Luke, starting from the same pericope in Mark s Gospel, also
makes 18 changes, but all of them different! Thus are created 36 points of difference
between the Majors, and so, more explanations will need to be sought.
So there are two approaches to explanation: (a) Matthew and Luke