I can imagine Luke standing still, looking at the saber, asking Rey: "Who are you? ... And where did you get that?" Rey replies "It found me, it showed me... things. It brings bad luck to the weilder." Luke tells her: "There's no such thing as luck..."
Rocks raise, and fly toward Rey, she activates the saber, slicing and blocking every rock thrown in her direction. Luke says "you have natural skill, let's improve, starting now."
Rey deflects rocks with one hand, spins around and force throws the rocks back toward Luke. Luke drops the cloak, a green blur is seen, dust explodes as he powerfully yet precisely swings his green lightsaber through the wall of rocks.
They stare at eachother, both shocked yet impressed. "Good. You're taking your first steps. You will find the force is everywhere, flowing through you, guiding you on your journey. That lightsaber didn't call to you alone, the force called to you, too. You have a very strong connection with them."
Rey: "Tell me about the force. The jedi."
Luke: "I can't tell you. But I will show you the force. And each side it resides on.. Clear your mind.. Relax... Breathe... Just breathe..."