The Levites Emerge
The incident of the Golden Calf, was the defining moment when the Levites demonstrated their deep commitment to the Jewish people. They were chosen to replace the First Born in doing Temple service.
There were many Jews aside from the Leviim that did not participate in this grievous sin. The Chidushei Rim points that relative to the population, a small number lost their lives.
The others that stood on the sideline did not have the strength and courage of the Levites. They were the ones who answered Moshe’s call of מי לה׳ אלי, “Whoever is for Hashem, join with me.”
Many thought that it would not be wise to be part of a conflict. They stood by and watch the situation unfold. The Leviim took action in restoring the honor of Hashem. They took swords in their hands, to fight the idol worshippers.
It is for this reason that Hashem later declared, והיו לי הלויים, “And the Levites shall be with Me.” They showed the faith and commitment necessary to become true servants of G-d.