Related על ראש השנה 3:7

Did a shepherd leave his cattle behind the synagogue or was a sick person lying behind the synagogue, [and] he has the sound of the horn or heard the voice of the [recitation of the Esther scroll, if he has set his heart to it, he has done his duty; but if not, he has not fulfilled his duty. Although one heard [the sound] and the other heard [the sound], [there is this difference]: one has set his heart on it, but the other has not set his heart on it; he who has set his heart on it has done his duty, but he who has not set his heart on it has not done his duty. Everything depends on the heart being set on it; for it is said: ”You set their heart [to it]; you let your ear pay attention”, and she says [further]: “Give me, my son, your heart and let your eyes pay attention to my ways !”