מרבים העם להביא מדי העבדה למלאכה… איש ואשה אל יעשו עוד מלאכה לתרומת הקדש (ויקהל לו:ה-ו)

The passuk says that the Chachamim who built the Mishkan came to Moshe and said, מרבים העם להביא מדי העבדה למלאכה “The Yidden are bringing too much.” Moshe heard them and said to announce, איש ואשה אל יעשו עוד מלאכה לתרומת הקדש “Everyone should cease working on the Mishkan.” Only then did the people stop bringing any further donations.

If the Chachamim said that too many donations were coming in, why did Moshe command to stop working on the Mishkan? He should have said to stop bringing donations.

The Sefer Sifsei Tzaddikim tells a story about the holy Apta Rav zt”l, who answered this question with a story.

The shamash in the city of Apta (Opatów, Poland) used to knock on the doors of the Jewish inhabitants to wake them up to go to Shul for Shacharis. When people heard the shamash banging with his hammer in the middle of the night, they could not fall asleep again or even stay in bed. They would jump out of bed and run to the Beis Medrash to learn or recite Tehillim in preparation for the morning prayers.

The shamash was not an outstanding Talmid Chacham. He was a simple, devout Yid.  However, in his younger years, he served as the shamash – personal assistant to the holy Reb Shmelka zt”l of Nikolsburg (Mikulov, Czech Republic).  Since he did his work so piously and devotedly, this caused his knocking on doors to have the Yidden arise to עבודת הבורא – the service of Hashem.

The Apta Rav zt”l concluded: The same was true for building the Mishkan.  When Yidden heard the noise generated by Betzalel and the other artisans building the Mishkan, it aroused the hearts of the Yidden to bring in unlimited donations.  Thus, Moshe understood that it was of no use telling the Yidden to stop bringing donations, for as long as they heard the banging of the hammers, they would get more and more… therefore Moshe called out to stop building the Mishkan so that the Yidden would stop bringing donations.