'Milk' in the Bible

I fed you with milk, not solid food; for you were not yet able to receive it. Even now you are still not ready.

[Consider this:] Who at any time serves as a soldier at his own expense? Who plants a vineyard and does not eat its fruit? Or who tends a flock and does not use the milk of the flock?

For though by this time you ought to be teachers [because of the time you have had to learn these truths], you actually need someone to teach you again the elementary principles of God’s word [from the beginning], and you have come to be continually in need of milk, not solid food.

For everyone who lives on milk is [doctrinally inexperienced and] unskilled in the word of righteousness, since he is a spiritual infant.

like newborn babies [you should] long for the pure milk of the word, so that by it you may be nurtured and grow in respect to salvation [its ultimate fulfillment],