[י' אייר תשי"ח]
... ומובן וגם פשוט, שכיון שזכה שהשגחה העליונה העמידתו על חלק היפה, עבודה בחינוך הכשר על טהרת הקדש, המקרב לב התלמידים לאבינו שבשמים, בודאי שזהו מברר ומזכך ומעלה מדרגא לדרגא התלמיד והמתחנך ומוסיף בהצלחתו של המחנך והמלמד בעצמו, וכמו כל עניני האדם, שעל כל אדם נאמר בכל דרכיך דעהו, הרי גם זה צ"ל בשמחה וטוב לבב, שהרי ציווי השי"ת הוא קיום התורה והמצוה וגם בכל דרכיך דעהו, וק"ל.
B"H, 10 Iyar 5718.
It is understood and also obvious that since you have merited that Divine Providence has placed you in the fortunate position of working in kosher education, pure in holiness, which brings the hearts of students closer to our Father in Heaven, certainly this clarifies, refines, and elevates both the student and the one being educated from level to level, and increases the success of the educator and teacher himself. As with all matters of a person—about whom it is said: "Bechol Derachecha Da'eihu" ("In all your ways know Him")—so too this must be done with joy and a good heart. For the command of Hashem is to fulfill Torah and mitzvahs, and also "Bechol Derachecha Da'eihu" ("In all your ways know Him"). And this is clear.
Summary
Teaching Torah with purity not only uplifts students but also refines the educator. The Rebbe teaches that such holy work must be performed with joy and wholeheartedness, as every aspect of life should be permeated with awareness of G‑d.