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..(Mat 17:20)
And he said, The things which are impossible with men are possible with God.(Luk 18:27)
This was the faith of Joshua and Caleb when they were faced with the walls of Jericho.