Rashi on Exodus 26:30/רש"י על שמות כ״ו:ל׳

1והקמת את המשכן AND THOU SHALT SET UP THE TABERNACLE — after it is completed set it up. ...

2הראית בהר This must be translated: WHICH THOU WILT before then HAVE BEEN SHOWN IN THE MOUTAIN — (The verb is future perfect). For later on I shall instruct thee and show thee the way to erect it.