רַ֚ק אִם־שָׁמ֣וֹעַ תִּשְׁמַ֔ע בְּק֖וֹל יְהוָ֣ה אֱלֹהֶ֑יךָ לִשְׁמֹ֤ר לַעֲשׂוֹת֙ אֶת־כָּל־הַמִּצְוָ֣ה הַזֹּ֔את אֲשֶׁ֛ר אָנֹכִ֥י מְצַוְּךָ֖ הַיּֽוֹם׃
if only thou diligently hearken unto the voice of the LORD thy God, to observe to do all this commandment which I command thee this day.
Sifrei Devarim
(Devarim 15:5) "Only if you hearken to the voice of the L-rd your G-d": From here they stated: If a man hearkens but a little, he is given to hear much. If he hearkens to the words of Torah, he is given to hear the words of the scribes.