Rashi on Exodus 34:35/רש"י על שמות ל״ד:ל״ה

1והשיב משה את המסוה על פניו עד באו לדבר אתו MOSES REPLACED THE VEIL UPON HIS FACE UNTIL HE CAME IN TO SPEAK WITH HIM — but when he came in to speak with Him he took it off his face.