Distinctions between Belief, Believe and Faith pt. 2

​Another passage to consider is Matthew 17:20 - So Jesus said to them, “Because of your unbelief; for assuredly, I say to you, if you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you. Jesus made a similar statement in Luke 17:6.
 
Obviously, this is a figure of speech as a mustard seed doesn’t have faith so we’re left to figure it out.  So, my first observation is that unbelief (Greek apistia) and faith (Greek Pistis) are both nouns.  So, Jesus wasn’t referring to how strongly they believe, but rather the content of what they believed.  Faith is based on knowledge Biblical faith on God’s word as explained in Romans 10:17 “so then faith comes by hearing, and hearing by the word of God.”  You can’t believe what you do not know. 
 
So, figuratively what does a mustard seed know?  That it can sprout and grow into a mustard plant.  That is the complete content of its purpose and knowledge.  I believe what the Lord was saying here is simply this, if you know what God wants you to do then you can do it.  The Disciples had been given the power to cast out demons in Chapter 10 when Jesus sent them out to the cities in Israel.  Here in Matthew 17 a man came and asked the disciples to cast a demon out of his son, but they could not.  Why not?
 
Well, this took place on the day after the transfiguration.  Peter, James and John had gone up the mountain with the Lord for that event.  And according to Mark this man brought his son the 9 disciples who stayed behind.  When the father showed up with his son a group of Scribes were in a debate with those disciples.  That may be a factor in their failure to cast out the demon.  Based on Christ’s mustard seed illustration I suspect those scribes had shaken the disciple confidence thus fomenting the failure.  Of course that is just speculation on my part, but Jesus Christ did say their failure was due to their unbelief.  
 
For some reason those 9 disciples could not do what they once had be able and it was due to unbelief.  I’m sure they tried.  I would guess they really wanted to help this man.  But it didn’t require effort or strong desire. It only required they believe the right thing.  My guess is they forgot something Jesus Christ had told them back in chapter 10.