Rashi on Exodus 34:10/רש"י על שמות ל״ד:י׳

1כרת ברית [BEHOLD, I] MAKE A COVENANT about this.

2אעשה נפלאת — The word נפלאת is an expression of the same meaning as ונפלינו (Exodus 33:16; so that the phrase means: I will make a difference) meaning that you shall be different in this respect from all other peoples — in that My Shechinah will not rest upon them.