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. (Matthew 17:20 NKJV)
As Jesus and three of His disciples were coming down the mountain after the transfiguration, a father comes up to Jesus for healing for his son. The disciples that were at the bottom of the mountain couldn’t heal the boy. After Jesus healed the boy, the disciples asked why they were unable to heal him. Jesus said it was because of their unbelief. Don’t give up if you think your faith is not strong. Little faith, as a mustard seed, can grow.