Verses with the word faithless in the New Testament (4 verses):

Matthew 17:17
Then Jesus answered and said, O faithless and perverse generation, how long shall I be with you? how long shall I suffer you? bring him hither to me.

Mark 9:19
He answereth him, and saith, O faithless generation, how long shall I be with you? how long shall I suffer you? bring him unto me.

Luke 9:41
And Jesus answering said, O faithless and perverse generation, how long shall I be with you, and suffer you? Bring thy son hither.

John 20:27
Then saith he to Thomas, Reach hither thy finger, and behold my hands; and reach hither thy hand, and thrust it into my side: and be not faithless, but believing.