The miracles in the Bible were a sign pointing to Christ, his life, and his work- that was their purpose. These signs were not performed by just anyone. What was the result of these signs fulfilling their purpose?
Even during their lifetime, the Gospel message to Israel and the whole world had been completely delivered and confirmed by God. At this, the Apostles emphasized that the integrity of what had been delivered must be guarded at all costs. This why scripture says the (definite article THE) Christian FAITH had been delivered once for all:
“Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints.” – Jude 1:3 (Emphasis Added)
This is also why the writer of Hebrews, in chapter 2, tells us about the delivery and confirmation of the Gospel as a done deal:
“So what makes us think we can escape if we ignore this great salvation that was first announced by the Lord Jesus himself and then delivered to us by those who heard him speak? And God confirmed the message by giving signs and wonders and various miracles and gifts of the Holy Spirit whenever he chose.” Hebrews 2:3-4 (Emphasis Added)
This is why the Apostle Paul lays the harshest curse on anybody or anything in heaven or on earth that will seek to alter the Gospel in any way:
I am astonished that you are so quickly deserting him who called you in the grace of Christ and are turning to a different gospel— not that there is another one, but there are some who trouble you and want to distort the gospel of Christ. But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed. As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed. – Galatians 1 (Emphasis Added)
The Gospel, as delivered by the Apostles, is a finished work. It has a definite start and endpoints. It has also been confirmed as being of divine origin by the mighty signs performed by the Lord and his sent ones.
Their mission was fully accomplished.
Therefore all that is left for us believers is to place our faith in it – bank our very lives on it – obey it, live by it and guard it from distortion, addition, or subtraction, including updates of any kind.