Moshe, speaking to Bnei Israel about the Torah before his demise, states that it is not in the heavens nor overseas but: כִּי קָרוֹב אֵלֶיךָ הַדָּבָר מְאֹד בְּפִיךָ וּבִלְבָבְךָ לַעֲשֹׂתו, “Rather, the matter is very near to you, in your mouth and in your heart, to perform it.” (Deut. 30,14) We see in this verse a connection between the mouth, the heart, and performance.
It speaks to everyone. There are Jews to whom Judaism is connected only to the mouth. They publically proclaim that they are Jewish. There are Jews who add to that their heart. They give charity and similar deeds but executing Mitzvot is not part of their performance. They believe that you can be Jewish with only the mouth and the heart but need not consider the Mitzvot.
Both of these views err critically. Being Jewish requires fulfillment with all your body and all your faculties. The psalmist says: כָּל עַצְמוֹתַי תֹּאמַרְנָה, “All my bones shall say…”, (Psalms 35,10) We also recite this verse every Shabbat and holiday morning when we say נשמת. This verse implies that practicing Judaism requires our entire body and our total ability. The mouth and the heart and the Mitzvot are all part of being Jewish.