It is notable, though, that various important manuscripts and diverse early witnesses omit these words. Therefore, Matthew 17:21 lacks adequate ancient textual support.
The variant reading is well-supported by a variety of manuscripts, including 𝔓100, and is the reading that most English versions followed. However, …
The process of attempting to ascertain the original wording of a text is important, regardless of how minor the textual variant may seem. Our primary purpose is to give the Bible readers what God said by way of his human authors, Our primary goal is to be accurate and faithful to the original text. Therefore, we must have the original words.
Originally, all New Testament texts were written in Greek. By the year 500, these texts had been translated into Syriac, various Coptic, Latin, Gothic, Armenian, Georgian, and perhaps Ethiopic dialects. This article is a great introduction for those just learning about New Testament Textual Studies.
What is the original reading: (1) “you may devote yourselves to prayer” or the longer (2) “you may devote yourselves to fasting and to prayer”?
What is the original reading: (1) “This kind does not come out except by prayer” or the longer (2) “This kind does not come out except by prayer and fasting”?
The reading απεστερημενος (“having been withheld by fraud”) or αφυστερημενος (“having been withheld”) is a bit of a hand ringer because of the split evidence.
Because there are so many individual manuscripts, textual critics are hard-pressed to know the individual characteristics of each manuscript. Consequently, many textual critics categorize the manuscripts into text-types, which they then use in their evaluation of textual variants.
Kurt Aland (1979, 43) favors a type of textual criticism that he calls the local-genealogical method. He defines it as follows: