Mark
King James Version (KJV)

“And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;”
King James Version (KJV)
16:17 And these signs shall follow them that believe - An eminent author sub - joins, That believe with that very faith mentioned in the preceding verse. (Though it is certain that a man may work miracles, and not have saving faith, #Matt 7:22|,23.) It was not one faith by which St. Paul was saved, another by which he wrought miracles. Even at this day in every believer faith has a latent miraculous power; (every effect of prayer being really miraculous;) although in many, both because of their own littleness of faith, and because the world is unworthy, that power is not exerted. Miracles, in the beginning, were helps to faith; now also they are the object of it. At Leonberg, in the memory of our fathers, a cripple that could hardly move with crutches, while the dean was preaching on this very text, was in a moment made whole. Shall follow - The word and faith must go before. In my name - By my authority committed to them. Raising the dead is not mentioned. So our Lord performed even more than he promised.
Mr 16:17 These signs shall follow them that believe. It is generally held that this is a promise limited to the apostolic age and to a few of the disciples of that age. Perhaps the plural "them" does not have for its antecedent the singular "he" in Mr 16:16, but the plural "them" in Mr 16:14. If it does not, why is the number changed in Mr 16:15,16? The grammatical construction requires us to look to Mr 16:14 for the antecedent of "them" in Mr 16:17. In Mr 16:14 the apostles are "upbraided for their unbelief because they believed not them who had seen him after he had arisen". They are commended to go and tell the glad story, and assured that miraculous credentials shall be given to those of "them who believe" and tell the wonderful tidings. In my name shall they cast out demons, etc. See Mr 16:14-16 Ac 2:4 5:16 8:7 16:18 28:3.