It is like things that you bring out of a room where you keep them. The good man says good things because he keeps good thoughts in his mind. The bad man says bad things because he keeps bad thoughts in his mind. Matthew 12:35
善人從他心裏所存的善就發出善來；惡人從他心裏所存的惡就發出惡來。 馬太福音 12:35