He was seen teaching Rey how to use the force. He told her to kill him if she can. Of course, she cannot and said the force is strong with him as well as his foot. Then he said he can teach her. but she has to chop her arm off. He explained his father cut off his arm off. Then Rey's master chopped off Rey's hand quickly with his lightsaber and gripped a baseball with the force.
Rey's jedi training