וְיִסְּד֥וּ הַבֹּנִ֖ים אֶת־הֵיכַ֣ל יְהוָ֑ה וַיַּעֲמִידוּ֩ הַכֹּהֲנִ֨ים מְלֻבָּשִׁ֜ים בַּחֲצֹֽצְר֗וֹת וְהַלְוִיִּ֤ם בְּנֵֽי־אָסָף֙ בַּֽמְצִלְתַּ֔יִם לְהַלֵּל֙ אֶת־יְהוָ֔ה עַל־יְדֵ֖י דָּוִ֥יד מֶֽלֶךְ־יִשְׂרָאֵֽל׃
And when the builders laid the foundation of the temple of the LORD, they set the priests in their apparel with trumpets, and the Levites the sons of Asaph with cymbals, to praise the LORD, according to the direction of David king of Israel.
Rashi on Ezra
And...laid the foundation וְיִסְדוּ This is the strong conjugation of יְסוֹד, like (Ezek. 25:4): “and they will settle (וְיִשְּׁבוּ) their palaces.” Just as וְיִשְּׁבוּ is derived from ישּׁב so is וְיִסְדוּ derived from יסד, and their meaning is, וְיִסְדוּ וְיִשְּׁבוּ in the intensive conjugation with two “yud”s, one for the [continuous] action and one for the radical, and their meaning is that they were laying the foundation, they were settling.
Rashi on Ezra
And the builders laid the foundation And the builders were laying the foundation [see above] of the Temple of the Lord at the time [that] they were harmonizing in their song, and they stationed the priests attired with elegant garments with trumpets in their hands to sound them.