Mark 9:20

9:20 So they brought the boy to him. When the spirit saw him, it immediately threw the boy into a convulsion. He fell on the ground and rolled around, foaming at the mouth.

Mark 9:18

9:18 Whenever it seizes him, it throws him down, and he foams at the mouth, grinds his teeth, and becomes rigid. I asked your disciples to cast it out, but they were not able to do so.”