Mishkan For All

The Rosh says that the teruma of זהב כסף נחושת alludes to three types of giving tzedakah.  There is the gold level of tzedakah when one gives out of their own volition, the silver level when one gives in a situation of distress and the נחושת level when one gives charity already on the deathbed.  

There are three opinions as to when the commandment to build the Mishkan was said.  Rashi (Ki Sesa 31:14) says it was said after Klal Yisrael were forgiven for the agel on Yom Kippur.  The Ramban's opinion is that the commandant to create the Mishkan was said before the agel but the donations were collected only afterward and the Zohar is of the opinion that the donations for the Mishkan were collected before the sin of the agel.  These three opinions, says the Rebbe (Likutay Sichos volume 6,) represent three types of Jews that all participated in the Mishkan.  The opinion of Rashi is that the Mishkan is donated by balei teshuva, the Jews after they were forgiven for the agel.  The Zohar's approach is that the Miskan was given when Klal Yisrael were tzaddikim, had not sinned at all.  The opinion of the Ramban is that the commandment of the Mishkan remained throughout the sin of the agel, representing reshaim.  All three are needed and have a place in their lives for the Mishkan.  All three need a place for kedusha in a physical form that they can access and contribute to.  The Rebbe adds these three correspond to the זהב כסף ונחושת for כסף related to chesed is the avodah of tzaddikim, zahav related to din is the avodah of balei teshuva and nechoshes related to the word nachash is related to the reshaim.  The first three donations correspond to the three groups of Klal Yisrael all represented in the building of the Mishkan. 

This may line up with the forms of tzeddakah the Rosh says is alluded to in the possuk.  The tzaddik gives tzeddakah without any external push, the bal teshuva gives when they are stuck like doing teshuva after a sin and the rasha gives only at the very end of his life, he doesn't want to take away from his own enjoyment when he could use the money for himself.