Midrash Rabbah Shir haShirim on Words of Torah in the Heart

" 'The heart of a wise man enlightens his mouth, and adds learning on his lips' (Proverbs 16:23). The heart of a wise man is full of wisdom. Who enlightens others about him? Who informs others about him? His mouth. When he speaks words of wisdom, his mouth informs others of him; his mouth apprises others of him. '... and adds learning on his lips'. Because the wise man extracts the words of Torah from his heart and enunciates them with his lips, he adds to the learning of Torah."

-- Midrash Rabbah, Shir haShirim 1.6

Sefer haZohar on Aspiration of the Heart

"Happy are the righteous who know how to focus the aspiration of their hearts on the Holy King, and whose hearts' intention is not at all directed to this world and its vain desires; rather, they know and strive to direct their will and cleave above, drawing the will of their Lord to them from above to below. Where do they obtain the will of their Lord, drawing it to them? From a certain supernal holy place, whence issue all holy desires. And who is this? This is 'kol ish (every man)' ─ master of the house, whose desire is constantly for Matronita, like a man who loves his wife. Incessantly, his heart impels him ─ He loves Her, and his heart, His Matronita, is impelled to cleave to to Him."

-- Sefer haZohar, 2:134b (transl. D. Matt)