Rabbi Yehudah ben Ilai makes a disturbing claim in the Mekhilta: idolatry crossed the Red Sea with Israel. The very nation that had just witnessed God's greatest miracle — the splitting of the sea, the destruction of Egypt's army — carried idol worship through the waters alongside them.
The proof lies in a creative reading of the verse. "And Moses removed Israel from the Red Sea" can also be read as "And Moses removed from Israel the thing of the Red Sea." What was this "thing"? It was idolatry — the Egyptian religious practices and objects that some Israelites had clung to even through the plagues, even through the Exodus, even through the parting of the waters.
Zechariah provides the prophetic confirmation (Zechariah 10:11): "And tzarah passed through the Red Sea." The word tzarah literally means "rival" or "adversary," and the rabbis identified it as a code word for idolatry — the rival to God's worship, the adversary of true faith.
This is a sobering teaching. The Red Sea did not purify Israel of their Egyptian influences. The miracle of the crossing did not automatically erase generations of living among idol-worshippers. Moses had to actively remove the idolatry after the crossing. Faith is not something that happens to you because you witness a miracle. It is something that must be deliberately chosen, and the old attachments must be deliberately stripped away — even on the far shore of the greatest wonder in history.