Such a blatantly obvious copy there by Mark, really!
(48) say(s) IS : "should" two make-be peace with their(.PL) companion in this-one house alone they will tell it to the mountain : turn outward and he will turn
(106) say(s) IS : when you(PL) continue-to make-be the two one you(PL) will come-to-be the(PL) child of the human and in-case you(PL) continue-to tell it : oh mountain turn outward he will turn
(Mark 11:23 For most certainly I tell you, whoever may tell this mountain, 'Be taken up and cast into the sea,' and doesn't doubt in his heart, but believes that what he says is happening; he shall have whatever he says.)
(Luke 17:6 The Lord said, "If you had faith like a grain of mustard seed, you would tell this sycamore tree, 'Be uprooted, and be planted in the sea,' and it would obey you.)
(Matthew 17:20 He said to them, "Because of your unbelief. For most certainly I tell you, if you have faith as a grain of mustard seed, you will tell this mountain, 'Move from here to there,' and it will move; and nothing will be impossible for you.
(...)
21:21 Jesus answered them, "Most certainly I tell you, if you have faith and don't doubt, you will not only do what was done to the fig tree, but even if you told this mountain, 'Be taken up and cast into the sea,' it would be done.)
In Mark the mountain moving into the sea is highly likely inspired by Psalms 46:2, but Luke replaces the mountain by a sycamore tree: 7 mentions of those in the Tanakh, and it is apparently a very common tree bearing figs: Kings, Chronicles and Isaiah 9:10 mention it. Matthew copies the logion twice, once coming up with the rather unimaginative 'Move from here to there'
Speaking to a mountain is unique and mentioned only in Thomas, where obviously the mere action of moving a mountain is the monumental achievement - where it moves to is completely irrelevant. Mark trying yet one more time to combine his two goals (incorporate Thomas and refer to scripture) in one sentence distracts Matthew here, and it is one of the rare occasions on which Matthew disappoints from a semantic point of view. He does get it right in his chapter 21 although he evidently feels like he still has to move the mountain somewhere
It is a very nice evolution that we see here. Thomas has his own context (
if you make the two one you can achieve anything, even far beyond what is deemed possible) and the mere moving of the mountain; Mark wraps only the moving mountain in his context and unfortunately suffixes it with the actions of (not) doubting, and believing.
Luke spots that weakness and has the stress on faith precede the commanding of the inanimate object, and comes up with the beautiful find of the phrase 'faith like a grain of mustard seed' - which is a cringing allegory but can be allocated value if we acknowledge the way in which the gospel-writers interpreted the parable of the mustard seed. Does the mustard seed tempt Luke to use the sycamore tree instead of the mountain? Isaiah chapter 9 of course is a very important chapter:
(Isaiah 9:2 The people who walked in darkness have seen a great light. The light has shined on those who lived in the land of the shadow of death.
(...)
6 For a child is born to us. A son is given to us; and the government will be on his shoulders. His name will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.
(...)
9 All the people will know, including Ephraim and the inhabitants of Samaria, who say in pride and in arrogance of heart, 10 "The bricks have fallen, but we will build with cut stone. The sycamore fig trees have been cut down, but we will put cedars in their place.")
It would be surprising to find Luke quoting scripture all by himself, I think?
Matthew puts the mountain back in, opting for the so very poor move phrase, but cherishes Luke's find and keeps the 'faith as a grain'. And in his second attempt combines it all: Luke's 'faith', Mark's 'doubt', his context at that moment which is the cursed fig tree, and the original first copy of Mark
On this occassion, it is very likely that Luke came after Matthew - but where did he get the uprooted from?
