Mark 13:11 promises that followers of Jesus will be given words by the Spirit to speak when they stand before civil and religious authorities in the context of persecution. Below is but a brief theological explanation as to why this promise is not for us today but for those in the Tribulation, a time of judgment that ends this age. A practical note is given at the end.
Jesus promised the apostles that “the Spirit of truth” would “guide you into all the truth” (John 16:13). In Revelation, the last book of the Bible (chronologically and canonically), John warned that God would judge the one who “takes away from the words of the book of this prophecy” (Rev 22:19), and he also warned that God would judge the one who “adds to them,” that is, “the words of the prophecy of this book” (Rev 22:18). God thus effectively commanded through John that no additional prophecies were to be given, now that the canon was complete with the book of Revelation. In terms of John 16:13, “all the truth” had been given. It follows that, as the book of Revelation circulated to all the churches with its command to add no more words to its prophecy, so also did any valid claim to the reception and communication of special revelation (a.k.a., prophecy).
Dismissed by the view above are two contemporary views of “non-normative” prophecy (i.e., prophecy binding for those who receive it but not the church at large). One is that prophecy exists today, but is something less in quality than prophecy by OT prophets or the apostles. This revelation could be received without error but then errantly delivered to others. The fault here is that the end result is not revelation if it is something errant but yet from God. Another view is that the gift of tongues carries on today, whether in congregational worship (assumedly alongside the gift of interpretation), evangelism, or private prayer. But if the Spirit is at work to control the language, so also is He involved in giving the words, which is tantamount to prophecy. But if prophecy has ceased, then all gifts pertaining to tongues have ceased as well.
Concerning the Tribulation, a seven-year period of judgment that precedes the millennial reign of Christ on earth, this period is marked by prophecy throughout, an expression of God’s mercy and grace since the church and pillar of truth will have just been raptured into the presence of the Lord Jesus Christ (cf. 1 Thess 4:13–5:11). Among other instances of prophecy that could be noted, it begins with the arrival of two prophets who prophesy (Rev 11:3). Followers of Jesus who are called before the authorities will be given words by the Spirit to speak at that time (Matt 10:20; Mark 13:11; Luke 12:12). The Spirit is poured out on sons and daughters who shall prophesy as well (Joel 2:28)
If a word from God is verbal or written, the authority is the same because these words are from God. A disagreement over the above, then, is to disagree on the matter of authority. Either God speaks today through His written Word, or He speaks through His written word and words He gives to others. If His Word indicates that others do not receive revelation today (as explained above), then we should not believe any claims that God has spoken beyond His written Word.