The Essence of Judaism (parshat תרומה)

Why three when you can use just one?

It would seem more fitting to build Hashem’s house out of just gold, since gold is the finest and most beautiful of these three metals, and the Jews definitely had enough gold to make a Mishkan entirely of just that metal. Why, then, were silver and copper also used in the construction of the Mishkan?

3 kinds of metals, 3 types of Jews, 3 ways of serving Hashem

Each of the three metals, gold, silver and copper, can be compared to a different type of Jew.

Silver in הקודש לשון is כסף, which is also the root of the word נכספים, which means to desire - Tzadikim, who are constantly yearning to be close to Hashem, are the silver.

זהב​- Gold - We know that even the greatest צדיק cannot reach the closeness to Hashem that a תשובה בעל can reach. For this reason תשובה בעלי are the gold, because they are considered greater than tzadikim, and gold is more valuable than silver.

Copper in הקודש לשון is נחשת, which has the same root as the word נחש, snake. When ב"י sin, they are following the הרע יצר like the snake which caused the first sin.

Everyone counts

The Mishkan was built by the entire congregation, which is called a צבור in הקודש לשון. The letters of the word צבור stand for the words צדיקים בינונים ורשעים, referring to all different types of Jews. This teaches us that a tzadik shouldn’t think that those lower than him can’t be involved in serving Hashem and a rasha shouldn’t think that he has no place in Hashem’s house. Hashem instructed ב"י to use all three kinds of metal because Hashem wanted all types of Jews to join together to build the Mishkan and to take part in serving Him. Only when all ב"י are doing their part, from the greatest tzaddik to the lowest rasha, will Hashem rest His Shechina within the us.

(Lubavitcher Rebbe; Likutei sichot vol 6 pages 152-161)