שִׁבְעַ֣ת יָמִ֗ים יִלְבָּשָׁ֧ם הַכֹּהֵ֛ן תַּחְתָּ֖יו מִבָּנָ֑יו אֲשֶׁ֥ר יָבֹ֛א אֶל־אֹ֥הֶל מוֹעֵ֖ד לְשָׁרֵ֥ת בַּקֹּֽדֶשׁ׃
Seven days shall the son that is priest in his stead put them on, even he who cometh into the tent of meeting to minister in the holy place.
Rashi on Exodus
שבעת ימים SEVEN DAYS in succession, on such a High Priest’s installation,
Rashbam on Exodus
ילבשם הכהן, the newly appointed High Priest is to wear them prior to his being inaugurated.
Siftei Chakhamim
[They must be] consecutive. [Rashi knows this] because otherwise, why does it say “seven days”? A Kohein Gadol must wear these garments every time he serves, after which he removes them [until the next time]. Perforce, it refers to his seven days of installation — which are consecutive.