How do we know Mark 16 ends at verse 8 and not 20? The two best available Greek manuscripts of the New Testament, Codex Sinaiticus and Codex Vaticanus do not have either the usual 12 verse ending or the shorter ending. Neither does manuscript 304, the Sinaitic Old Syriac, some manuscripts of the Sahadic Coptic version, manuscripts of the Armenian translation, and some versions of the Georgian translation. It is significant that it does not appear in any manuscript prior to the fifth century. This passage is included in a number of other, later manuscripts, but with critical marks such as asterisks or obeli (marks to indicate that a passage is spurious, doubtful or corrupt), which tell us that the scribe knew of the questionable nature of these verses. The shorter ending is found in some less important manuscripts. In some other manuscripts, this shorter ending is combined with the longer ending. Codex W, an important early Greek manuscript, adds an entire paragraph between verses 14 and 15. All of this together is strong proof that Mark 16:9-20 was not originally part of Mark’s Gospel. Bible scholar and translator Jerome, around 400 CE, said “Almost all the Greek codices (are) without this passage”.
Possibly even a bigger problem for anything after Mark 16:8 than the manuscript evidence, or lack thereof, is the variety of different endings. These make no sense if verses 9-20 were part of the original Gospel of Mark. If Mark 16:9-20 was authentic, then there would not be all these various endings. The variety of endings are extremely strong proof that Mark originally ended at 16:8. These endings were obviously added later, so they would not be genuine.
Additional evidence against verses 9-20 is that the vocabulary, syntax and theological content are radically different from the genuine part of Mark’s gospel. The natural reading of these verses strongly implies that whoever wrote them originally wasn’t entirely familiar with the entire book of Mark and the other gospels, and was using apocryphal (false) and extraneous sources. Verse 9 introduces Mary Magdalene as though she is being introduced to the reader for the first time, although she was mentioned just 8 verses previously, in 16:1, as well as in 15:40,47. She is also mentioned in Matthew 27:56,61, which was probably written some years before Mark’s gospel, possibly 20 years prior to Mark.
Verses 17 and 18 have Jesus promising: “These signs will follow those who believe (implying ALL who believe): In My name they will cast out demons; they will speak with new tongues; they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay their hands on the sick; and they will recover” (NKJV). NLT says: “They will be able to handle snakes with safety”. These verses are similar to many apocryphal (false) writings that were circulating in the 2nd and 3rd centuries. The NT records no Christian drinking deadly poison, much less recovering. 1 Corinthians 12:29,30 notes that some early Christians spoke in tongues, and had other miraculous gifts, it impresses the point that not all did so. 1 Corinthians 12:31-13:3 emphasizes that these were not the greatest gifts, but love is. 1 Corinthians 13:8-13 stresses that these miraculous, but lesser, gifts would pass away once “completeness comes” (NIV), apparently the complete NT. The point is that the spurious promise of Mark 16:17,18 is contradicted by other scriptures, those which are actually inspired by God.
Deuteronomy 4:2 and Rev 22:18,19 warn about the seriousness of ‘adding to’ God’s word. Mark 16:9-20 et al is a notable example of such ‘adding to’. Therefore, we would do well not to use these verses as though they were “the word of God”, since they are “a human word” (1 Thessalonians 2:13 NIV). This is especially true if we take to heart the serious warning at Revelation 22:15 about those who ‘like and carry on falsehood’, which Mark 16:9-20 is!