Doubt appears in the Epistle of James, in Jesus’ words to Peter on the water, and in the cry of the father in Mark 9.
In James 1:6:
6 But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed.
In Matthew 14:31:
31 And immediately Jesus stretched forth his hand, and caught him, and said unto him, O thou of little faith, wherefore didst thou doubt?
In Mark 9:24:
24 And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.