שימו לבבכם. צָרִיךְ אָדָם שֶׁיִּהְיוּ עֵינָיו וְלִבּוֹ וְאָזְנָיו מְכֻוָּנִים לְדִבְרֵי תוֹרָה, וְכֵן הוּא אוֹמֵר "בֶּן אָדָם רְאֵה בְעֵינֶיךָ וּבְאָזְנֶיךָ שְׁמַע וְשִׂים לִבְּךָ" (יחזקאל מ'); וַהֲרֵי דְבָרִים קַל וָחֹמֶר וּמַה תַּבְנִית הַבַּיִת שֶׁהוּא נִרְאֶה לָעֵינַיִם וְנִמְדָד בְּקָנֶה צָרִיךְ אָדָם שֶׁיִּהְיוּ עֵינָיו וְאָזְנָיו וְלִבּוֹ מְכֻוָּנִין, לְהָבִין דִּבְרֵי תוֹרָה שֶׁהֵן כַּהֲרָרִין תְּלוּיִין בִּשְׂעָרָה עַל אַחַת כַּמָּה וְכַמָּה (ספרי): שימו לבבכם SET YOUR HEARTS [UNTO ALL THE WORDS WHICH I TESTIFY AGAINST YOU THIS DAY] — Indeed, it is necessary for a man that his eyes, his heart and his ears, should all be attentively directed to the words of the Torah, for so it states, (Ezekiel 40:4) “Son of man, behold with thine eyes, and hear with thine ears, and set thine heart [upon all that I shall show thee]” (viz., the plan of the Temple). If in the case of the model of the Temple, which was being made visible to the eyes and was being measured by a rod, it was necessary for a man, according to Scripture, that his eyes, his ears and his heart be attentive, then in order to understand the words of the Torah which are like mountains suspended on a hair (i.e., numerous laws are derived from a single word of the Torah), how much the more is this necessary!