Nachman of Breslov,
Likutei Moharan — 5
“ And when you guard your brain from the aspect of Chametz, to not be obstructed, that your voice will hit your skull and produce thunder, and the crookedness in your heart be shed, then you will attain joy, as written, "Uliy'shrei-lev simchah/And joy to those who are straight of heart." ”
