Rashi on Deuteronomy 12:13/רש"י על דברים י״ב:י״ג

1השמר לך TAKE HEED TO THYSELF [LEST THOU OFFER THY BURNT OFFERINGS IN EVERY PLACE THAT THOU SEEST] — This negative form of the positive command in v. 11, is stated in order to attach a negative command (לאו) to this matter (Sifrei Devarim 70:1).

2בכל מקום אשר תראה IN EVERY PLACE THAT “THOU” SEEST — i.e., that enters thy mind, but thou mayest offer anywhere by the command of a prophet, as, for instance, Elijah did on Mount Carmel (1 Kings 18:21 ff.) (Sifrei Devarim 70:3).