The question is asked -- how old did Adam and Chava look when they were created? Were they babies? Did they have the appearance of people in their 40’s?
The Midrash (Bereishis Rabbah 14:7) brings in the name of Rabbi Yochanan the view that Adam and Chava had the appearance of 20-year-olds when they were created.
Additionally, beyond this Midrash, it’s clear from the Talmud (Rosh Hashanah 11a) that everything in Creation was made full and complete. The language there states, “They were created with their full stature, with their full intelligence, and with their full measure of beauty.”
And why was this?
The simplest reason given is so that all of Hashem’s creations – ranging from lions to human beings – could fend for themselves in a way that a cub, chick, or newborn baby cannot.
Simultaneously, there is also a deeper explanation given: For a person to be motivated to do, build, make, create, and nurture, he must first have a vision of what the finished product is supposed to look like. That’s just the way we’re wired. So, too, at the Creation of the world, Adam needed a vision of what a perfected person – and indeed the world – was supposed to look like. This would then enable him, in the future, to know what he needs to build towards.
Amazingly, this theme appears once again in the Chumash (Parshas Terumah), in reference to an incident in the construction of the Mishkan. Rashi, based on Midrash Tanchuma (Beha’aloscha 3), notes that the verse there doesn’t instruct, “Make the Menorah,” but uses a more passive tense, saying, “shall the Menorah be made.” Why the passive tense?
Astonishingly, the answer is because the Menorah was made on its own! Moshe was perplexed as to how to make it, so Hashem showed him an image of a Menorah of fire, showing what it was supposed to look like. He still couldn’t do it, so Hashem had Moshe throw the gold into the fire and it was made by itself. So why was Moshe asked to make something he couldn’t make? If Hashem knew he wasn’t going to be able to, why did he show him the image?
The answer is the same as above: you can’t even possibly begin to build unless you first have the finished form in mind!
I would also add parenthetically that I believe very strongly that the reason Hashem has instructed each of us to have a Rabbi, or other qualified spiritual guide ("Aseh L'cha Rav"), is for a very similar reason.
We must have in front of us an image of what we should be building ourselves towards, whether in Torah knowledge, character traits, fear of Heaven, and in Bein Adam L’Chaveiro (how we treat one another).
Like Adam HaRishon and Moshe Rabbeinu, just because we see the vision doesn’t mean we’ll be ultimately successful in recreating it. However, we cannot get down to the work of building without it!