25 Then he said to them, O fools, and slow of heart to believe all that the prophets have spoken:
Luke 24:25 Cross References - RKJNT
Mark 7:18
18 And he said to them, Are you also without understanding? Do you not perceive, that whatever enters into the man from without, it cannot defile him;
Mark 8:17-18
Mark 9:19
19 He answered him, and said, O faithless generation, how long shall I be with you? how long shall I endure you? bring him to me.
Mark 16:14
14 Afterward, he appeared to the eleven as they sat eating, and rebuked them for their unbelief and hardness of heart, because they did not believe those who saw him after he had risen.