Found this commentary, about Matthew 17:21, interesting:
This verse is omitted in many good manuscripts and by the Revised Version, it being considered to have been introduced from the parallel passage of St. Mark. It gives the second reason for the failure of the nine. This kind... fasting. Though all things are possible to faith, some works are more difficult of accomplishment than others. This kind can mean only this kind of evil spirit, or demons generally. But the latter interpretation is excluded by the fact that the apostles had already exercised successfully their power over devils without special prayer or fasting. The words point to a truth in the spiritual world, that there are different degrees in the Satanic hierarchy (comp. Matthew 12:45); some demons are more malignant than others, and have greater power over the souls of men.
(con't) (post 1 of 2)

(con't) (post 2 of 2)
In the present case the possession was of long standing; it revolved a terrible bodily malady; it was of an intense and unusual character. The mere word of exorcism, or the name of Jesus, spoken with little spiritual faith, could not overcome the mighty enemy. The exorcist needed special preparation; he must inspire and augment his faith by prayer and self-discipline. Prayer invokes the aid of God, and puts one's self unreservedly in his hands; fasting subdues the flesh, arouses the soul's energies, brings into exercise the higher parts of man's nature. Thus equipped, a man is open to receive power from on high, and can quell the assaults of the evil one.

https://biblehub.com/matthew/17-21.htm

Our published versions of "the bible" are without doubt incomplete works from selected texts.
A compendium of writings purposed towards attaining a compliant populace. Unquestionably there is plagiarism. However, our marvelous creator has bestowed communion, conscience and intuition within our spirit and soul to intelligently divide the truth as it resounds.

ONLY THROUGH A RELATIONSHIP WITH HIM JESUS YOU GAIN WISDOM. THE BIBLE IS THE LIVING WORD. OUR FATHER MISSES YOU. TIME IS SHORT. HE WANTS TO HEAR FROM YOU. GOD BLESS ALL.

they have been changing words for a while..folks who read the book(s) have done vids of words swapped out, ie the mark of the beast became IN not ON...never read any so cannot tell you which version /book it was.
.vids - were on YT.

Also, The Lords Prayer, different versions either say 'On earth as it is in heaven' or 'In earth as it is in heaven'. I have three versions and one if different from the other two.

👍👀🔥💥just checked the one that i read out of...and it is missing...this is crazy !...thank you for the post...that's why i wonder sometimes if even the words were changed througout time

unbelievable...glad it helped.

it keeps getting more and more unreal.

God Bless.

"They" don't want you to PRAY AND FAST. Not under our watch, Satan. You lost BIGLY!

Some people seem to accept the explanation that this is covered in other books/verses.

Repetition is important and so is context.

FYI. I have it in some of my older KJV bibles.

When studying for ministry, and having taken greek for the New testament, i learned a little about this.

Supposedly we do not have any original texts of any of the Bible. What we have is copies, and copies made of copies, and copies made of those copies. We have alot of them and they all do not agree. There are people who go through these copies and decide based on what they find decide which copies are most accurate. I believe this field is called "Textural criticism". My Greek New Testament has many many scriptures with footnotes denoting alternate reading or translations where these people could not make up their mind what should really be there.

It tiktok vid, the NIV has a [21]. That denotes that they were not sure if it should be there are so the scripture is down in the footnotes at the bottom of the page probably with an explanation like "earliest manuscripts omit this verse."

This is actually happens with modern translations alot.

I prefer KJV for study