[It should be noted that, while the covenant is an eternal and inviolable covenant,
which God never nullifies, it is possible for those who are in the covenant to break it.
If one who stands in the legal covenant relationship does not enter upon the covenant life, he is nevertheless regarded as a member of the covenant. His failure to meet the requirements of the covenant involves guilt and constitutes him a covenant breaker,
Jer. 31:32;
Ezek. 44:7. This explains how there may be, not merely a temporary, but a final breaking of the covenant, though there is no falling away of the saints./QUOTE]
Jer31;
32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt;
which my covenant they brake, although I was an husband unto them, saith the Lord:
here is ezk 44;
7 In that ye have brought into my sanctuary strangers, uncircumcised in heart, and uncircumcised in flesh, to be in my sanctuary, to pollute it, even my house, when ye offer my bread, the fat and the blood, and they have broken my covenant because of all your abominations.
So until you give me actual page numbers, I say that you are simply guessing. You have nothing from Berkhof.
I would say that you have guessed wrong, and that indeed we have something from Berkhof.
If Nicodemus was in the covenant and we have no evidence he was a covenant breaker and committed apostasy.....why would you assume he was an unsaved person.
Now I grant you that he did not understand God's grace in how the new birth took place. Many on BB seem to lack this understanding also. That is why Jesus teaches the teacher in Israel. He comes to Jesus and had some questions....but Jesus knew what he needed. Jesus corrects his misunderstanding in no uncertain terms. You can call it evangelism if you want to, that does not disturb me......but Nicodemus had obeyed all the external rituals that he was brought up with, he like the Jews in jn 8 thought they were okay, but they were not, and at this point it looks as if he was not yet in the clear.
Before we go down this road, you have to clarify what you mean by "covenant." Abrahamic? Mosaic? Davidic? One of the three (or two, depending on the author) made-up covenants of covenant theology? Once you define how you are using the term "old covenant" then we can discuss it. I assume you are referencing the only time the term occurs in the whole Bible (2 Cor. 3:14), but I don't know what your understanding is of that.
Covenant theology is a thread all by itself, in fact that would be several threads. Here I was thinking of Abrahamic, and Mosaic.
My point in bringing this up was not to veer off into such a discussion, but rather a little investigation shows Nicodemus was not outside the Covenant, but needed some work on Deut 30:6 perhaps, so Jesus addressed that directly;
6 And the Lord thy God will circumcise
thine heart, and the heart of thy seed,
to love the Lord thy God with all thine heart,
and with all thy soul, that thou mayest live.
A look at the reformed and presbyterian model of understanding the covenant is helpful to see what it was like for OT persons who were in the Covenant.....It was breakable, and some will contend it is still the same model and breakable, in that there were unsaved persons said to be "in the Covenant'....as Baptists we do not hold to this and part ways with them on this.