The Jewish nation enthusiastically contributes materials for construction of the Mishkan. “And the princes [of the twelve tribes] brought the onyx stones and the stones for the settings of the Ephod and the Choshen…” [Exodus 35:27]
The princes said, “Let the public donate what they will, and we will make up the shortfall.” When the public completed all [that was necessary]… the princes said, “What is [left] for us to do?” [So] they brought the onyx stones….And because they were lazy at the outset, a letter was omitted from [the spelling of] their name [in the Torah scroll, in the above verse.]
[Midrash, cited by Rashi]
The princes should be given credit for their generosity! They intended to step forward and pick up the slack for the entire nation. Why are they instead accused of laziness?
The princes believed their offer stemmed from generosity (and undoubtedly intended to make good on their promise.) But G-d, who sees the subconscious mind, testified that their underlying motivation was not absolutely pure. Pure generosity would have led the princes to contribute immediately. Their decision to wait was colored by an infinitesimal drop of laziness. In the end, the princes were left with little to contribute.
The princes were men of exemplary character, and believed their behavior reflected sincere generosity; in reality, their judgment was skewed by a thread of simple laziness. If these great individuals erred due to a subconscious bias, we are certainly susceptible to misjudgments based on our own hidden flaws. If we engage in honest introspection, we can trust that G-d will help us reach conclusions that are wise and authentic.