Answer

ANSWER:

The פסוק concludes with the words וֹבַד עוֹד מִלְ אֵין , there is none other besides Him.

When Hashem punished the Egyptians and took בני ישראל out of מצרים, they only saw that Hashem is greater and stronger than the Egyptians. This might leave them thinking that there might be other powers, although Hashem is the greatest and most powerful.

Therefore, רש"י explains that it refers to what they were shown at הר סיני, when Hashem opened the heavens, and there they saw that וֹבַד אֵין עוֹד מִלְ , there is none other besides Him.

As רש"י concludes, at הר סיני they saw they He is יְחִידִי, the only One.