Why did Moshe have the voice of a grown up boy?

Question

Shemos 2:6 states:

וַתִּפְתַּח֙ וַתִּרְאֵ֣הוּ אֶת־הַיֶּ֔לֶד וְהִנֵּה־נַ֖עַר בֹּכֶ֑ה וַתַּחְמֹ֣ל עָלָ֔יו וַתֹּ֕אמֶר מִיַּלְדֵ֥י הָֽעִבְרִ֖ים זֶֽה׃

When she opened it, she saw that it was a child, a boy crying. She took pity on it and said, “This must be a Hebrew child.”

Rashi there explains:

והנה נער בכה. קוֹלוֹ כְּנַעַר :

והנה נער בכה lit., AND BEHOLD A BOY WEEPING — Although he was a ילד, “a child”, his voice was like that of a נער, a grown up boy.

Rashi on the Gemara in Sotah which makes the same point makes it very clear that it is an older boy:

נער - גדול משמע:

What on Earth is the point of Moshe's voice sounding like a grown up boy? There must be some very serious significance which necessitated this miracle but I don't have the faintest idea what it could be.

(It would have been very clear to everyone that he wasn't actually an older boy since there is no indication that he looked like an older boy so this could not possibly have been to trick Bas Pharaoh into thinking he was born before the decree.)

Answer 1

This may very well be one of Ramban's objections to Rashi's explanation:

ועוד מה טעם שיזכיר הכתוב עובי קולו

And furthermore, what reason is there that Scripture should mention the thickness of his voice?

While this is not quite asking why it should have occurred in the first place, it is similar to your question in that it sees no point for this.

However, there are a couple of explanations offered by the later commentaries.

R. Judah Loewe explains that this was engendered by God for this specific instance in order to cause Pharaoh's daughter to take pity on him; i.e. had he sounded like a regular baby she would not have taken pity on him:

ויראה שלא היה זה במשה בטבעו ולא היה זה אלא לשעה מגיד לך שהיה בוכה בכי גדול בקול גדול והיה מאת הקב"ה כדי שתחמול עליו

And it appears that this was not in Moses naturally; this was only for the moment, to tell you that he was crying a great cry with a great voice, and it was from God so that she would take pity on him.

He doesn't explicitly state why this type of crying would be more likely to invoke the pity of Pharaoh's daughter, but from the way he describes it as "a great cry" he might mean that it was exceptionally loud for a baby, and had he merely cried like a regular baby Pharaoh's daughter would not have noticed it.

R. Ephraim Luntschitz actually explains this in line with your rejected suggestion:

וי"א שלכך נשמע קולו כנער כדי שתחשוב בת פרעה שנולד מזמן רב דאל"כ לא תציל אותו מספק כי שמא הוא הגואל ונולד באותו יום שאמרו האצטגנונים

And some say that for this [reason] his voice was heard like a na'ar — in order that the daughter of Pharaoh should think that he was born a while ago. For if not [for this] she wouldn't save him, out of concern that he might be the redeemer and was born on the day the astrologers said.

Answer 2

Yalkut Reuveni and Baal HaTurim state that the pasuk, V’hinei naar bocheh, “And behold! A youth was crying,” refers to Moshe’s older brother Aharon. That is, Aharon was standing with Miriam and crying over Moshe. Aharon three years old, but he was had accompanied Miriam to watch over Moshe. Since the Jewish People did not adopt Egyptian styles, it was obvious that the boy who was standing guard over Moshe, and who was crying out of fear for the infant, was none other than Aharon, a Jewish boy. If he was Jewish, it made sense that the infant was also Jewish.

The explanation that Moshe sounded older was in order to say that he cried in a manner to arouse sympathy. a screaming infant might have repulsed the daughter of Par'o so that she would not have been willing to pick him up.