Oh, that gospel; the occasional pastoral letter
gospel that saint Paul wrote to some very strange Corinthian Christians who had a hard time treating one another well at their celebrations of the Lord's supper and who were very confused by spiritual gifts, so let's have a look at what it says and if it teaches what you were advocating before - namely
that people play no role whatever in salvation.
Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain.
For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures, and that he appeared to Cephas, then to the twelve. Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep. Then he appeared to James, then to all the apostles. Last of all, as to one untimely born, he appeared also to me. For I am the least of the apostles, unworthy to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me. Whether then it was I or they, so we preach and so you believed.
(I Corinthians 15:1-11)
First saint Paul observes that his readers are
being saved by a gospel in which they stand. His wording suggests some continuation of belief is needed to eventually receive the salvation which is some kind of process that the Corinthian Christians are undergoing - hence believing the gospel is something by which they are being saved rather than something that they believed once and were saved by it back then and now are enjoying their salvation without any need to believe anything or do anything. So saint Paul goes on to say
if you hold fast to the word I preached to you and adds that their previous belief could be in vain unless they hold fast to the message that he preached before by believing it.
Next saint Paul rehearses the core content of is message, namely that
that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures, and that he appeared to Cephas, then to the twelve. Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep. Then he appeared to James, then to all the apostles. Last of all, as to one untimely born, he appeared also to me. The people to whom the risen Lord appeared are included as evidence that Jesus really did rise from the dead - 1 Corinthians 15 is about the resurrection so it is necessary to establish that Jesus really did rise from the dead because if he didn't then saint Paul points out that the gospel is a lie and believing it is pathetic. But it is worth noticing what saint Paul says is the core message:
that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures. Here we see that the core events of the gospel message are about Jesus and not about us or anyone else. Just about Jesus and what he did that was in accord with the holy scriptures. The holy scriptures are, in this context, the old testament scriptures rather than the as yet nonexistent Christian scriptures of the new testament. So if Paul wanted to make the case that the Corinthians Christians have no role whatever in salvation then he would want to make that point here by asserting that there is nothing whatever that they (the Corinthians Christians) need do to receive the benefit of the gospel message that saint Paul preaches. Well, is that what he says?
No, it is not what he says. He already said that the gospel message that he preached has to be believed and persistently believed so that one's salvation can be brought to completion and then, after mentioning the witnesses to the resurrection and his own place in that group, he writes about himself and the Corinthian Christians that the grace given to him was not lazy but
On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me. Whether then it was I or they, so we preach and so you believed. Saint Paul's message is clear enough; he urges continuation in steadfast believing and the conduct that such belief implies so that the initial belief of the Corinthian Christians would not be in vain. He wants his readers to understand that Jesus Christ is the one who saves and that believers are to accept that and live a life of devotion to the Lord so that their belief will not be in vain. So yes is the answer to the question "must I
do something in order to be saved".