Parashas Naso
וַיְהִ֡י בְּיוֹם֩ כַּלּ֨וֹת מֹשֶׁ֜ה לְהָקִ֣ים אֶת־הַמִּשְׁכָּ֗ן וַיִּמְשַׁ֨ח אֹת֜וֹ וַיְקַדֵּ֤שׁ אֹתוֹ֙ וְאֶת־כׇּל־כֵּלָ֔יו וְאֶת־הַמִּזְבֵּ֖חַ וְאֶת־כׇּל־כֵּלָ֑יו וַיִּמְשָׁחֵ֖ם וַיְקַדֵּ֥שׁ אֹתָֽם׃
On the day that Moses finished setting up the Tabernacle, he anointed and consecrated it and all its furnishings, as well as the altar and its utensils. When he had anointed and consecrated them,
Torah Temimah points to TT / related (verified).
ויהי ביום כלות משה להקים — תניא, כל שבעה ימי המלואים היה משה מעמיד ומפרק את המשכן, וביום השמיני העמידו ולא פרקו.
English: “On the day Moshe finished erecting” — it was taught: Throughout the seven days of inauguration Moshe would erect and dismantle the Mishkan; on the eighth day he erected it and did not dismantle it.
Custom
Chazal describe the sevenfold erecting and dismantling before the final permanent standing of the Mishkan.