For they considered not the miracle of the loaves: for their heart was hardened.

This is speaking of his disciples who were with him in the boat; notice it said  'their'  heart was 'hardened'.  Now why was their heart 'hard'?

The Scripture teaches that those under the law had a hard heart.  Remember, he prophecied that he would give them a 'heart of FLESH'  [not stone] and write His words on their heart. [His Word cannot be written on their heart of stone = they cannot receive the Word as long as the  LAW is in their heart;  for this makes them have this heart of stone = law]

Wow!!!!!!!   What a revelation!!!!   God just showed me this.  Glory, Isaiah!

Their heart was hard IF  the LAW  is there;  because the LAW  was written on  STONE!   God said he would take out of them the STONY HEART   and give them a heart of flesh.  The  STONY  heart is the one the law is in!!  So this is saying  God wanted to take the LAW  out of their heart.  People  if the law is in your heart, you have the heart of  STONE;  for the  STONE  means the law.  That is why God wrote the law on stone;  to show that the law turns one to stone.

The disciples at that time were still under the law;  so they had a hard heart.  That is WHY  they did not have faith.  Remember, Jesus kept rebuking them for their 'little' faith?

But look at them after the Holy Ghost is in them~~~~~  Great men of faith~~~insomuch that Peter's shadow healed people.

Eze: 

011:019

And I will give them one heart, and I will put a new spirit within you; and I will take the stony heart out of their flesh, and will give them an heart of flesh:   036:026 A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. Matt. 13:5--Some fell upon  STONY places, where they had not much earth;  and forthwith they sprung up, because they had no deepness of earth: v6--And when the sun was up, they were scorched; and because they had no root, they withered away. People, this is saying that as the NT Word was sown, some fell into those with the stony heart of the law, and they had no ROOT in themselves;  because God had up-rooted that old law and done away with it.  So, when the 'sun' [=Jesus' power] was up, they 'scorched' and withered away. God had left them no root = no life in that law.  This matches the parable of the plant which bore no fruit and they uprooted it and threw it into the fire.  That old law 'vine' bore no fruit to God [remember, we have showed that many times in this study on law;  that they bore no fruit;  they were an empty vine (Hos.)] So, it was without any root therefore could not endure the 'sun' light = Jesus' NT words. = Grace. They had no 'deepness' = no depth.  They can not receive deep revelation of the Word.  I am seeing this PROVEN right here in this community--- those who believe in the LAW  cannot receive the deep revelation of the Word.  They cannot belive for healing.  They have NO  ROOT. Their 'heart' is stone = the LAW. Mark 4:5-  also said some of the seed = word;  fell on stony ground.  This stony GROUND  is their heart of stone = heart of LAW. Thank you God, for giving me a heart of flesh;  soft, pliable Potter's Clay.  Mold me and make me into the image of your dear Son. JO