He is not afraid because his friend Faithful reminds him of the words of Psalm 23 : Yea , though I walk through the valley of the shadow of death , I will fear no evil : for thou art with me ; thy rod and thy staff they comfort me . When he is in the middle of the valley amidst the gloom and terror he hears the words of the Twenty-third Psalm , spoken possibly by his friend Faithful : Yea , though I walk through the valley of the shadow of death , I will fear no evil : for thou art with me ; thy rod and thy staff they comfort me .