Now… you gladdened my heart by informing me that you began to learn matters of mussar and fear of heaven with your students, wisdom from holy books; fortunate is your lot. Surely this is particularly necessary at this time and in this country, where the transient cravings for the vanities of the world, jealousy, desire, honor and the like, are so loud and clamorous. How can we stir the hearts of youths that they should open their eyes to see the glory and splendor, the brilliance and majesty of the Torah, if not by studying the discipline of genuine piety from the works of the great authorities of Israel, who delved into the wisdom of piety profoundly and expansively …?
I am unable at this time to offer you an orderly account of the ideas that are appropriate for your dear students. And it is especially difficult to specify the holy ideas in accordance with the level of the students, as I am not familiar with their state of mind and emotional strengths. Nevertheless, it would appear that, first of all, you ought to explain to all the students the fundamental principle that any success in Torah, sense of accomplishment in study … and one day achieving a high level in the crown of Torah – depends on the measure of fear of heaven and the depth of pure and holy faith that is implanted in one's soul. For the broadening and deepening of the intellectual faculty, its brilliance and its branching out in many directions, which is the great foundation for sharpness and fluency, depends on the depth of emotional will that awakens to value what is being studied. Since he is occupied with Torah, which is the word of the living God, the quality of the inner appreciation of his occupation with Torah depends on the sanctity of true fear of God that rests in the heart of him who is occupied in the Torah. For to the extent that the fear of heaven becomes strengthened in one's heart in sanctity and purity, so too the words of the Torah, which are the light of the countenance of the living king, become precious and elevated in one's eyes. And owing to their great dearness, inner desire attaches to them, and it is the nature of inner desire to arouse all of the soul's faculties with life, joy and good-heartedness, with great desire and the pleasantness of high and lofty spiritual delight. And since the soul's faculties are aroused - through the expansion of the holy quality of the fear of heaven - to love for the Torah and passion for all its words, and cognition grows from day to day…, the soul's faculty of memory is greatly strengthened, from the life force that the sacred desire for the Torah stirs up in the soul that contemplates genuine fear of heaven. And from the great respect and elevated value that he assigns to the words of the Torah, which grows every day in accordance with the fear of heaven that grows in his heart from day to day, as he continually occupies himself in the holy study of the true fear [of heaven] and its branches - his intellectual diligence is strengthened, the brightness of his mind grows, and true sharpness and sound reasoning increase.
It turns out, then, that the best advice for the students to succeed in their study, that their learning should be blessed and stay with them, and that they themselves should experience satisfaction and delight from their study, is to broaden their hearts every day with the study of the pure fear [of heaven]. All of its disciplines and all study of the soul and of character traits are offshoots branching out from the root of the elevated fear of God, which leads to perfect love of God, love of the Torah and its commandments, and love of Israel . (Responsa Da'at Kohen, no. 51; Iggerot ha-Ra'ayah, no. 798)
[Translation Vbm-torah.org]