קבלה אויף תהילים 2:11

R. Isaac opened his discourse with the text: “Serve the Lord with fear and rejoice with trembling.” We also read: “Serve the Lord with gladness, come before him with singing.” These verses seem to contradict one another. But the truth is that “Serve the Lord with fear” means that all service which a man renders to his Master should begin with fear and awe of Him, and through this fear he will come to perform the precepts of the Torah with joy.

[In his study,] the student must combine fear and joy, as it is written, rejoice with trembling (Ps. 2.11). [He must] add modesty to these two virtues. The reason for the combination of these three virtues [is this]: He requires [the virtue of] fear lest he err and sin. Moreover, he is delving [in his studies] in the place of the flame of the fire of joy, which matter, I have heard, requires prayer [for success]. Also, the Torah certainly depends upon [the virtue of] joy.