The Torah portion begins with an accounting of the Israelites’ contributions that were earmarked for construction of the Tabernacle, and precisely how those funds were utilized in practice. The Sages explain that it was necessary to prepare a detailed reckoning because there were those who maligned Moses, accusing him of misappropriating some of those funds.

“These are the reckonings of the Tabernacle” (Exodus 38:21). Why did Moses prepare a reckoning for them? The Holy One, blessed be He, trusted Moses, as it is stated: “Not so My servant Moses; in all My house he is trusted” (Numbers 12:7), and Moses said to the people: Come and prepare a reckoning with me! Moses heard the Israelites speaking behind his back, as it is stated: “It would be, upon Moses’ going out to the tent, that all the people would rise, and each would stand at his tent’s entrance; they would gaze after Moses” (Exodus 33:8). What were they saying? Rabbi Yitzhak says: They were speaking words of praise. They would say: Happy is the one who gave birth to him. All his days, the Holy One, blessed be He, speaks with him. All his days he is perfect in the eyes of the Holy One, blessed be He…. Rabbi Hama said: They were speaking words of deprecation. They would say: Look at the thickness of his neck, look at the girth of his thighs. He eats at the expense of the Israelites and he drinks at the expense of the Israelites, and everything that he has is from the Israelites. His counterpart would answer him: Wouldn’t you expect a person who controlled the Tabernacle project to be wealthy? When Moses heard that, he said to them: By your lives, once the Tabernacle is completed, I will prepare an accounting for you. (Tanĥuma [Buber], Pekudei)