Most modern English translations of the Bible place into brackets or footnotes the text of Mark 16:9-20, which is about Jesus appearing to the disciples and giving them instructions to carry on the work of preaching the gospel. The text records Jesus appearing first to Mary Magdalene who was not believed after telling others the news of Him being resurrected after His crucifixion. He then appears to two other disciples bodily and later for a third time to the eleven while they were supping. Scholars generally do not consider Mark 16:9-20 to be part of the original text of the gospel of Mark.
Two key witnesses consulted in reaching this conclusion would be Codex Sinaiticus and Codex Vaticanus. Their importance lies in them containing the oldest full copies of the Greek New Testament. In regards to textual defects, Randall Price writes, "...there are thousands of variants between them [Sinaiticus and Vaticanus], but where they agree they appear to represent a text that goes back to the second century AD" (Searching for the Original Bible, p. 80). Philip Wesley Comfort writes, "Through the use of chemicals and painstaking effort, a scholar can read the original writing underneath the printed text" (The Quest for the Original Text of the New Testament, p. 27, n 1).
Early Syriac, Coptic, Armenian, and Georgian translations are appealed to as evidence for Mark's gospel ending at 16:8. The New English Translation has this excerpt on Mark 16:9-20: "Most mss include the “long ending” (vv. 9-20) immediately after v. 8 (A C D W [which has unique material between vv. 14 and 15] Θ ƒ 33 M lat sy bo); however, Eusebius (and presumably Jerome) knew of almost no Greek mss that had this ending. Several mss have marginal comments noting that earlier Greek mss lacked the verses." This scribal interpolation was produced and in circulation as early as the second century. A few manuscripts contain a shorter ending that comes after Mark 16:8, which is cited as follows:
"And they reported all the instructions briefly to Peter’s companions. Afterwards Jesus himself, through them, sent forth from east to west the sacred and imperishable proclamation of eternal salvation. Amen."
Verses 12 and 13 parallels Luke 24:13-35 in which Christ chided two of His followers traveling on the way to Emmaus for their lack of faith. Verse 14 mirrors Christ appearing to the eleven apostles and eating with them in Luke 24:36-43 and John 20:19-23. Verse 15 is derived from Christ's commandment to preach the gospel to the unbelieving world in Matthew 28:18-20. Verse 16 echoes the words of incurred divine judgement on those who reject the gospel message found in John 3:18. The reference to handling snakes was gleaned from Paul's miraculous recovery from a snake bite during an encounter with barbarians in Acts 28. The idea of miraculous survival after drinking poison is nowhere to be found in the New Testament.
Contributor Walter W. Wessel writes in the Expositor's Bible Commentary on Mark 16:9-20 regarding differences in vocabulary and style when compared to Mark's gospel:
"Of the 75 significant words in v. 9-20, 15 do not appear elsewhere in Mark and 11 others have a different meaning. In other words, more than a third of the words are non-Markan. The marked difference in vocabulary between 16:9-20 and the rest Mark's gospel makes it difficult to believe that they both came from the same author."
The insertion of Mark 16:9-20 as a conclusion to Mark's gospel after verse 8 disrupts the flow of the narrative in that it is suddenly introduced and reads awkwardly. The use of the word "now" at the beginning of verse nine seems disconnected with the ending of verse eight for the reason that there is no smooth change in focus from the woman mentioned in Mark 16:8 to Jesus appearing to Mary Magdalene in Mark 16:9. Mark did not write his gospel in a choppy style. It would also be unusual for Mark to introduce in this place (as if it were for the first time) Mary Magdalene when she was already mentioned a few times before (Mark 15:40, 47; 16:1). Why is the detail of her having seven demons cast out by Christ brought up here?
The explanation taken here for Mark's gospel ending at 16:8 would not be that the concluding part of the work has been lost but he intended it to end that way. The theme of trembling and astonishment is one found throughout Mark's gospel (2:12; 4:41; 9:6; 10:32). The New English Translation has this footnote which speaks of, "the literary power of ending the Gospel so abruptly that the readers are now drawn into the story itself." It continues, "E. Best aptly states, “It is in keeping with other parts of his Gospel that Mark should not give an explicit account of a conclusion where this is already well known to his readers” (Mark, 73; note also his discussion of the ending of this Gospel on 132 and elsewhere). The readers must now ask themselves, “What will I do with Jesus? If I do not accept him in his suffering, I will not see him in his glory.”