Revelation shaped by our readiness

איתא בים נראה להם כבחור איש מלחמה ובסיני כזקן ז"ש אנכי על הים ובסיני כמ"ש רש"י ז"ל.

It is brought down that at the Yam Suf Hashem appeared to Bnei Yisrael as a young warrior, a man of war, while at Sinai He appeared as an elder. This is the meaning of "Anochi" — at the Sea and at Sinai — as Rashi explains.

Chazal teach that the same Hashem revealed Himself in two very different ways: as a mighty warrior when He fought for Bnei Yisrael at the splitting of the sea, and as a venerable, kindly elder when He gave the Torah at Har Sinai. The single word "Anochi" ("I am") contains both revelations.

והענין הוא שזה עצמו פי' אנכי ה' אלקיך שגילוי אלקותו ית' בעולם כפי עמידת בני ישראל.

The idea is that this itself is the meaning of "Anochi Hashem Elokecha" (I am Hashem your God) — that the revelation of His Godliness in the world is according to the spiritual standing of Bnei Yisrael.

The Sefas Emes explains that Hashem's appearance is not fixed; it is shaped by where Bnei Yisrael are holding. The verse "I am Hashem your God" teaches that the measure of divine revelation in the world corresponds to the readiness and condition of the people receiving it.

ולכן נגלה על הים בבחי' מלחמה ובסיני כזקן:

Therefore He revealed Himself at the Sea in the aspect of war, and at Sinai as an elder.

Because the revelation matches the moment, at the Sea — where Bnei Yisrael needed salvation from their enemies — Hashem appeared as a warrior, while at Sinai — where they were ready to receive Torah in peace and wisdom — He appeared as a wise elder.

Summary: The two contrasting images of Hashem — warrior at the Sea and elder at Sinai — both flow from the words "Anochi Hashem Elokecha," teaching that the form of divine revelation in this world is determined by the spiritual readiness of Bnei Yisrael.