Rashi on Deuteronomy 11:29/רש"י על דברים י״א:כ״ט

1ונתת את הברכה THEN THOU SHALT PUT THE BLESSING [UPON MOUNT GERIZIM] — Understand this as the Targum renders it: ית מברכיא those who pronounce the blessing.

2על הר גרזים means “towards Mount Gerizim”: they (the Levites) turned their faces towards it and began with a formula of blessing: “Blessed be the man that doth not make any graven or molten image etc.”. For each of the paragraphs beginning with the expression ארור as set forth in the chapter (Deuteronomy 27), they first recited in a converse form, beginning with the expression ברוך, “Blessed be etc.” and only afterwards did they turn their faces towards Mount Ebal and began to recite the corresponding curse (Sifrei Devarim 55:2; Sotah 32a; cf. Rashi on Deuteronomy 27).