תּוספֿתּא אויף משלי 23:26

One who blows while he is occupying himself [with the shofar], or one who blows while teaching himself [how to blow], or one who teaches his son, or one who teaches his student -- if he directed his heart [to fulfilling the mitzvah], he fulfilled it, and if not, he did not fulfill it. A shepherd that is watering his flock behind the synagogue, and so too a sick person who was brought behind the synagogue, or one whose house is adjacent to the synagogue, and heard the sound of the shofar, or the sound of the Megillah [being read] -- if he directed his heart, he fulfilled it, and if not, he did not fulfill it. Even though this one heard and that one heard, [since] this one directed his heart and that one did not direct his heart, the one who directed his heart fulfilled and the one who did not direct his heart did not fulfill, for everything follows after the direction of the heart, as it is said (Ps. 10:17), "Prepare your hearts, [and] incline your ears," and it says (Prov. 23:26), "Give me your heart, my son, and let your eyes observe my ways, etc."