Rashi on Deuteronomy 16:21/רש"י על דברים ט״ז:כ״א

1לא תטע לך אשרה THOU SHALT NOT PLANT THEE AN ASHERA — This is intended to make one liable to punishment regarding it from the very moment that he plants it (the Ashera); even though he does not worship it he transgresses a negative command by the mere planting of it (Sifrei Devarim 145:1).

2לא תטע לך אשרה כל עץ אצל מזבח ה' אלהיך THOU SHALT NOT PLANT THEE AN ASHERA, ANY TREE NEAR UNTO THE ALTAR OF THE LORD THY GOD — This is a prohibition addressed to one who would plant a tree or build a house on the Temple mount (הר הבית) (Sifrei Devarim 145:1).