Matt 17:19-20
19 Then came the disciples to Jesus apart, and said, Why could not we cast him out?
20 And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.
(KJV)
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Matt 21:21-22
21 Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done.
22 And all things, whatsoever ye shall ask in prayer, believing, ye shall receive.
(KJV)

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Matt 12:35-37
35 A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things.
36 But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment.
37 For by thy words thou shalt be justified, and by thy words thou shalt be
(KJV)

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Matt 15:16-20
16 And Jesus said, Are ye also yet without understanding?
17 Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?
18 But those things which proceed out of the mouth come forth from the heart; and they defile the man.
19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
20 These are the things which defile a man: but to eat with unwashen hands defileth not a man.
(KJV)

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Mark 7:20-23
20 And he said, That which cometh out of the man, that defileth the man.
21 For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders,
22 Thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness:
23 All these evil things come from within, and defile the man.
(KJV)