'Solid' 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.

For even though I am absent [from you] in body, nevertheless I am with you in spirit, delighted to see your good discipline [as you stand shoulder to shoulder and form a solid front] and to see the stability of your faith in Christ [your steadfast reliance on Him and your unwavering confidence in His power, wisdom, and goodness].

Such things are only a shadow of what is to come and they have only symbolic value; but the substance [the reality of what is foreshadowed] belongs to Christ.

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.

But solid food is for the [spiritually] mature, whose senses are trained by practice to distinguish between what is morally good and what is evil.

And the twelve gates were twelve pearls; each separate gate was of one single pearl. And the street (broad way) of the city was pure gold, like transparent crystal.