Мусар к Шмот 30:34

ואתה תצוה את בני ישראל. The word ואתה, occurs four times in connection with the construction of the Tabernacle and in each instance it appears to be superfluous. In Exodus 27,20, the word could have been omitted without changing the meaning of G–d's instructions to Moses. In 28,1 the Torah could have simply written: Karev! In 28,3 the Torah could have written: Dabber, and in 30,23 the Torah could have written: Kach lecha. We will concede that on the fifth occasion the Torah uses the word אתה, i.e. in connection with the commandment not to build the Tabernacle on the Sabbath (Exodus 31,13), there is some justification for use of the word אתה. G–d referred to the fact that Moses had a special standing relative to the Sabbath because it had been he who had chosen the Sabbath legislation while the Israelites were still in Egypt, something we mention every Sabbath morning in our liturgy when we recite: ישמח משה במתנת חלקו, "Moses rejoiced when he received his share, etc." The other four occasions when the Torah writes ואתה, present a serious difficulty.