מדרש על יחזקאל 44:5

(Devarim 32:46) "And he said to them: Put your hearts, etc.": We are hereby taught that one's eyes and heart and ears must be attuned to words of Torah. And thus is it written (Ezekiel 44:5) "And the L-rd said to me: Son of man, set your heart and see with your eyes, and hear with your ears all that I am saying to you about all the laws of the Temple … and set your heart to the entrance of the Temple and to all the exits of the sanctuary." Now does this not follow a fortiori? If re the Temple, which can be seen by the eyes and measured by the hand, one must "attune" his eyes and his heart and his ears — how much more so re words of Torah, which are like mountains hanging on a hair!