The incense was terrifying. Israel had watched it kill Nadav and Avihu, the sons of Aaron, when they brought unauthorized fire before God (Leviticus 10:1). Two young priests, dead in an instant, consumed by the very offering they presented. After that, the people drew a simple conclusion: the incense is an instrument of punishment. Stay away from it.
God wanted Israel to understand that they were wrong. The incense was not a weapon — it was a tool that could serve opposite purposes depending on the circumstances. To prove it, He would use the incense to save lives rather than take them.
The proof came during a devastating plague. When a deadly pestilence swept through the camp of Israel, Aaron rushed into the midst of the dying with his censer, burning incense among the people. "And he put on the incense and he atoned for the people" (Numbers 17:12). The same substance that had killed Aaron's own sons now stopped death in its tracks, standing as a barrier between the living and the dead.
The Mekhilta uses this to teach that nothing in God's world is one-dimensional. Fire burns and fire warms. Water drowns and water sustains. The incense destroys the unworthy and protects the faithful. The difference is not in the instrument but in the hands that wield it and the intention behind its use.