This might be controversial but Ursinus wasn’t infallible.
I say this because Article 31 of the Heidelberg Catechism and the exegetical work that underpins it is not fully fleshed out.
Q. What are the keys of the kingdom?
A. The preaching of the holy gospel and Christian discipline toward repentance. Both of them open the kingdom of heaven to believers and close it to unbelievers.
To be fair to Ursinus: he lacked the resources to truly understand the context behind what it was that Jesus instituted in Matthew 16:19. He saw the metaphor as any plain reader would and visualized a mansion with a door and that it was the responsibility of the church to keep unwanted visitors out.
Ursinus wasn’t even espousing anything radically new here. This understanding of the keys of the kingdom has been the longstanding backdrop for church order and canon law. There are times when, sadly, it is necessary for the health and function of the church that persons need be excluded.
I think that is established by Scripture in other places and through the exercise of wisdom. There are times where discipline is necessary and I don’t think anyone in the church believes that not to be true.
The Catechism is still misleading. The keys of the kingdom are not preaching and discipline. Finish the verse. Jesus tells us what they are:
I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.” (Matthew 16:19)
This is a particularly Jewish phrase that the early Church, which very quickly lost its Jewish nuance, failed to retain in its institutional memory.
It refers to the rabbinic practice of wrestling with questions of Torah and life. Life is wonderfully complex and, no matter how comprehensive your legal system is, there are always situations that require a more in-depth analysis.
Let’s keep it light in an example:
I cheer for a particular hockey team and, more than this, I consider it both an affront to God, humanity and all that is decent that anyone would cheer for another, very specific hockey team.
I believe that I have raised my children well. I have taught them in the ways that they should go and articulated clearly in both word and deed the impropriety and offence of venturing from the narrow way.
I have a child. She has strayed from the path. Had she simply chosen to support one of the other 29 teams in the NHL there would be no issue but she has decided that her team will be the forbidden team.
I believe that this is grounds to cast her out of the household or at the very least sacrifice a goat and publicly atone for her sin. She has violated the commandment to honour her father and mother. Fetch the rabbis.
They would hear my righteous plea. I would lay out my case before them and she her misguided allegiance and then they would deliberate and render a verdict.
They could bind or loose. Their decision could be to bind this under the Law. That is to say that what my daughter has done is what was intended by the commandment. Their decision could also be to loose this under the Law. Cheering for a bad hockey team was not what the Law intended and you’re free to do it.
Binding and loosing is the application of wisdom to the various circumstances of life where there is not a black and white answer prescribed by Scripture. The church receives this responsibility with the authority of heaven and earth. It gives gravity to the decisions made for the benefit of order within community.
Certainly when we consider the notion of discipline it can be found here: that in binding there is an expectation of adherence and the treatment of the pagan and the publican as consequence (Matthew 18:17).
The problem is that in framing the keys of the kingdom the Catechism has implied that the office of the church is simply to close the door.
We have focused so much on binding that it has become our ecclesiastical kink.
We’ve forgotten that it is also our task to loose. To examine the guests at the door and more than that to go out into the streets and find them (Matthew 22). To realize that they might be wearing a jersey that we don’t quite understand or even that we might not like but when we examine the evidence we realize that God hasn’t forbidden it in the dress code.
This is the preaching of the Holy Gospel. We defame the hospitality of God when we proclaim that you are not welcome here. When we assert what the Law does not say regarding our LGBTQ+ family who Jesus has invited to come. When we lock a door that was meant to be opened.
The preaching of the good news is that which frees from the bondage of sin and welcomes into the kingdom of God. It is one that opens that doors to the unexpected guest and dines with the pagan and the publican just like Jesus did.
An aside from Ursinus’ commentary and particularly relevant to our modern question:
Lastly, [discipline] should be so exercised as not to create any schism in the church, or be the occasion of any scandal, whilst good men see many at variance with each other, the church rent, and evils follow each other in quick succession. If the minister see or fear these evils he must not proceed, but warn and exhort both publicly and privately. And even though he may not be able to accomplish anything, he is still free from blame.