There is no greater trait than love of the Holy One, blessed is He, for all service of Hashem and all of Judaism stems from it. Now, love of God is one of the 613 commandments and it is a constant mitzvah which a person can fulfill at any time or moment by [merely] thinking about it. This commandment is fulfilled through thought and contemplation alone, for when one takes to heart that it is proper to love Hashem intensely, he thereby fulfills a very great mitzvah. These sort of commandments that are fulfilled through thought alone are easy to keep, for it is impossible for a person to not think at all even momentarily. [But] if one thinks about foreign thoughts or improper musings instead of love or fear of God, he thereby “forsakes the Source of living waters, to dig for himself broken cisterns” (cf. Yirmiyahu 2:13). It is therefore proper to gird oneself with much strength and fortitude to banish all foreign thoughts and improper musings, and instead think only holy thoughts.
י״ז בכסלו ה׳תשפ״ב
My brother and my nation, take this Torah book, in this and like this learn well, listen and revival your soul, you will achieve joy and joy, in this world and next world. (from introduction of the author) 1