This really is the Gospel in a nutshell, it doesn’t get any clearer than this, the gospel that Paul preached, which was received, by which you are saved.  The gospel which Paul also received; Christ died for our sins, was buried and rose again on the third day.  Notice there is no mention of your works saving you here, no mention of your baptism saving you, no mention of sabbath keeping here, no mention of anything but Christ and Him crucified, buried and rose again.  It is either all Christ or nothing at all, He saved you all by himself, and He keeps you saved all by himself.  Nothing that you or I can do will ever save us or keep us saved, we would still be dead in our sins if we had any part in it.

1 Corinthians 15:1-4

Moreover, brethren, I declare to you the gospel which I preached to you, which also you received and in which you stand, by which also you are saved, if you hold fast that word which I preached to you – unless you believed in vain.

For I delivered to you first of all that which I also received; that Christ died for our sins according to the Scriptures, and that He was buried, and that He rose again the third day according to the Scriptures, and that He was seen by Cephas, then by the twelve.