I'm still not sure I understand the question. Honestly, I've wondered about this very thing from the first time I made a more conscious decision to participate in this forum. Just what do folks consider "milk", or "solid food", or the "rudiments of the beginning of the Word of God"? I even asked the question years ago, but don't recall an answer that satisfied me.
You asked for a scriptural answer. This is I think the best of the translations I have in ESword. (Please don't leave out the first parts of the chapter that lead up to these.)
LITV Heb 5:12-14 For indeed because of the time you are due to be teachers, yet you need to have someone to teach you again the rudiments of the beginning of the Words of God, and you came to be having need of milk, and not of solid food; for everyone partaking of milk is without experience in the Word of Righteousness, for he is an infant. But solid food is for those full grown, having exercised the faculties through habit, for distinction of both good and bad.
"Partaking of milk" is done because one is an infant. "Infancy" is characterized by being "without experience" in the Word of Righteousness. Solid food is for those WITH experience, then...right? Full grown, having strengthened abilities through practice, for the ability to distinguish both good and bad--not simply the "difference between good and bad", but good and bad itself/themselves. Remember the fruit of the tree of the knowledge of good and evil? One fruit. We all eat it.
If I may reflect for a moment. There have been a lot of people come through this forum who seem to me to have failed to go on to being full grown. The ones that have made me the saddest are those who seem to have come to believe that their own "experience" pales to insignificance next to the pursuit of some theological bauble, or worldly curiosity, or "yet having need to have someone to teach them again". I'm not calling anybody out--because firstly I know that He is able to complete in everybody what He has started (indeed ONLY He is able), and secondly I ain't done yet either.
But I do wish they had a better idea of what "solid food" was and that many of them might remember that they have tasted it, even if they have returned to a more "milk-based" diet.
I'll finish with this. Since we are "HERE" and I'm not typing out to the whole word, I have what I think is a wise suggestion. Dig into the emails. They are full of "milky" questions. If you can answer them in a manner approaching the way Ray did, I'm willing to call you moving into "full-grown", without too much need of someone to teach you the rudiments, and no longer a babbling babe. And if you can answer from your own God-caused experience, even if you can't quote chapter and verse, then you're pretty much ready for anything, I think.