Which detail exemplifies the psychological distress that Ichabod experiences?

Ichabod experiences fear and apprehension in the grove. This line exemplifies the psychological distress that Ichabod experiences in the presence of the grove: "Once more he cudgeled the sides of the inflexible Gunpowder, and, shutting his eyes, broke forth with involuntary fervor into a psalm tune." Also, the narration describes how Ichabod speaks with "stammering accents," which shows his terror.