Two kinds of fear in avodah

בפסוק אל תיראו כו' יראתו על פניכם.

On the pasuk: "Do not fear… for His fear shall be upon your faces" (Shemos 20:17).

Moshe Rabbeinu tells Bnei Yisrael not to be afraid, yet in the same breath says that Hashem's fear should rest upon them — two seemingly opposite instructions.

ולכאורה הוא תרתי דסתרי.

At first glance these are two contradictory ideas.

How can he tell them not to fear and at the same time command that yiras Shomayim be upon them?

אך הענין שהיראה צריך להיות כדי שלא יחטא כמ"ש שיראה היא ליזהר ממל"ת.

But the point is that yirah (fear/awe) is meant to keep a person from sinning, as it is said that fear serves to guard one from transgressing the negative commandments (lo saaseh).

The proper role of fear is protective: it holds a person back from doing what Hashem forbade.

אבל לא שיתרחק ע"י היראה מעבודת הבורא יתברך.

But it is not meant to cause a person, through fear, to draw away from the avodah of the Creator, may He be blessed.

Fear must never become a wall that distances a person from serving Hashem; it should fence one off from sin, not from closeness to Him.

כמ"ש וירא העם וינועו כו' מרחוק.

As it is written: "And the people saw and trembled… and stood far off" (Shemos 20:15).

At Har Sinai the people were so overcome with dread that they recoiled and kept their distance — fear pushing them away rather than drawing them near.

וע"ז אמר להם מרע"ה אל תיראו:

And about this Moshe Rabbeinu said to them, "Do not fear."

Moshe corrected this misplaced fear: do not let awe drive you away — let it instead keep you from sin while you remain close in your avodah.

Summary: There are two kinds of fear. Healthy yiras Shomayim guards a person from sin, while a distancing fear pushes one away from serving Hashem. Moshe Rabbeinu taught Bnei Yisrael to hold the first and reject the second — keep His awe upon your faces, but do not let fear separate you from Him.