The Bible does not have to declare itself closed. Neither does it.
Yes it does. As has been pointed out: "If any man shall add unto the words of this book God shall add unto him..." The Book of Revelation, written ca. 98 A.D. was the last book of the canon of Scripture to be written, and thus that verse not only applies to Revelation but is applicable to all the Bible. It is a closed book. It declares itself closed.
Consider also that every time revelation was given by God it was accompanied by signs and miracles.
1. When Moses was given the Ten Commandments and wrote down the Law, he demonstrated that he was God's spokesmen by the signs and wonders that he did before Pharaoh. He also performed many more before the people of Israel as they wandered through the wilderness. He was the author of the first five books of the Bible. He was God's spokesman, and God gave him the ability to do signs and wonders to demonstrate that what he said were the very words of God.
2. Then came the prophets. Consider the miracles of Elijah and Elisha. Most of the writing prophets were contemporary with these men. These men were symbolic of all of the prophets. God gave them the ability to bring forth signs and wonders. Scripture was written during their lifetime and the lifetimes of the other prophets.
3. After the last prophet died there was a silence of 400 years when God did not speak to any prophet. The silence was deafening. No one received any revelation.
4. Then finally God broke his silence and raised up a prophet, the fore-runner of Jesus Christ, John the Baptist. During this time Christ was born. Many miracles were done by the hand of Christ and by his apostles. During the time of Christ and the Apostolic Age the NT was written. It was accompanied by signs and wonders. Those signs and wonders ceased by the end of the first century as canon of Scripture was completed, and closed. There is no more need of such spiritual gifts. They have ceased. We have the Bible instead. God has given us His Word.
God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,
2 Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds; (Hebrews 1:1-2)
--God did speak through visions, dreams, burning bushes, miraculous events, etc., but no longer. That age is past. He now speaks to us through His Son, as he is revealed to us through His Word.
Paul knew what the sign of an Apostle was, as he was one:
Truly the signs of an apostle were wrought among you in all patience, in signs, and wonders, and mighty deeds. (2 Corinthians 12:12)
--signs, wonders, and mighty deeds. These are not seen today.
The writer of the Book of Hebrews testifies:
How shall we escape, if we neglect so great salvation; which at the first began to be spoken by the Lord, and was confirmed unto us by them that heard him;
4 God also bearing them witness, both with signs and wonders, and with divers miracles, and gifts of the Holy Ghost, according to his own will? (Hebrews 2:3-4)
--God bore witness to the apostles signs, wonders different miracles, and the gifts of the Holy Spirit. These were all during the Apostolic Age of the first century. They are no longer in existence today, as we no longer have apostles today. They authenticated the apostles and their message and verified their message as the true message of God, setting them and their message apart from all others; all false messages. Theirs was from God.
The Bible has not been declared closed and gifts have no been declared ceased. "That"is most likely referring to the event rather than the person. As far as your "style" argument it is false to equate the context of "that" to a writing style.
In 1Cor.13:8ff., it speaks of spiritual gifts ceasing particularly tongues, prophecy, and revelatory knowledge. In verse 8 it says that they will cease. The only question is, when? The answer is: "when that which is "perfect" is come. The word perfect is in the neuter gender in the Greek, ruling out anything referring to Christ. The word "perfect" is the Greek word "teleios" other wise translated "complete." When that which is complete is come, then that which is in part shall pass away. There is a contrast here. There are partial or temporary gifts contrasted to semi-permanent gifts which in turn are contrasted to one permanent gift.
And now abideth faith, hope, charity, these three; but the greatest of these is charity. (1 Corinthians 13:13)
--The one gift that is permanent and that will continue on throughout eternity is love. It will never fail; it is the greatest of the three. It is permanent.
--Faith and hope are "semi-permanent," that is they too will end at some point in time. When? When Christ comes again. The Bible states that "we walk by faith and not by sight." When Christ comes we shall see him as he is. Faith will end. We will no longer walk by faith. We will see him. The same is true of hope. We hope for that which we see not. But when we see him we will have no more reason to hope. Hope will cease when Christ comes.
What about tongues, prophecy, and revelatory knowledge. They were temporary gifts that ceased when "that which was complete" (the Bible) came. There was no more need of them at that time. God gave to us his word and those gifts ceased. They ceased according to his word; they ceased according to history.
No one has ever demonstrated the gift of tongues since that time.
No one has ever demonstrated the gift of miracles since that time.
No one has ever demonstrated the gift of healing since that time.
No one has ever given any viable evidence since that time of the above sign gifts being performed--ever!
They have ceased.
