3.

The Discourse on Reasons

43. "Monks, considering three reasons, it is indeed fitting to expound the Teaching to others. Which three? One who expounds the Teaching becomes one who experiences the meaning and one who experiences the Teaching. One who hears the Teaching becomes one who experiences the meaning and one who experiences the Teaching. Both one who expounds the Teaching and one who hears the Teaching become ones who experience the meaning and ones who experience the Teaching. These, monks, are the three reasons, considering which it is indeed fitting to expound the Teaching to others." The third.