Revelation 13:5

And there was given unto him a mouth
The beast is said to have a mouth before, like the mouth of a lion, ( Revelation 13:2 ) ; but now he was moved and stirred up by the dragon, the devil, to open it, not only in a cruel and voracious way, but in a haughty, lying, and blasphemous manner: and this was given him, it was at the instigation of Satan, and by divine permission; his coming, speaking, and acting, were after the working of Satan, but not without the will of God; who, as he gave up many to a judicial blindness, to believe his lies and blasphemies, gave up him to speak them, as follows:

speaking great things, and blasphemies;
great swelling words of vanity; calling himself by high and lofty titles, as Christ's vicar, Peter's successor, head of the church, universal bishop promising great things to his followers, riches, honours, pleasures, pardons, and heaven itself; and uttering things of a blasphemous kind, or great blasphemies, the particulars of which are mentioned in ( Revelation 13:6 ) ; so the little horn, who is the same with the Romish antichrist, is said to have a mouth speaking great things, very great things, and his look more stout than his fellows, ( Daniel 7:8 Daniel 7:20 ) .

And power was given unto him to continue forty [and] two months;
to continue in being, or to continue blaspheming and speaking great things; and indeed, as long as he continues, he will continue blaspheming; as soon as he arose he had a name of blasphemy on his heads, and his mouth was immediately opened in blasphemy, and so it continues, and will to the end of this date. The Ethiopic version reads it, "and power was given to him to do signs, whatsoever he would"; miracles, lying signs and wonders; see ( Revelation 13:13 Revelation 13:14 ) . Some copies read, and so the Arabic version, "and power was given him to make war"; but he did not make war as soon as he arose, and so not all the time that is here allotted him; and the word "war" seems to be transcribed from ( Revelation 13:7 ) . The phrase rather intends his being, and the continuance and duration of it; which is the same period of time in which the holy city is trodden under foot by this beast, and the same with the 1260 days or years, in which the witnesses prophesy in sackcloth, and the woman, the church, is in the wilderness, ( Revelation 11:2 Revelation 11:3 ) ( Revelation 12:6 Revelation 12:14 ) ; for forty two months, reckoning thirty days to a month, as the eastern people did, make just 1260 days, for these things are all contemporary: hence it appears, that 1260 prophetic days, that is, years, contain the whole period of antichrist's reign and continuance; so that could we tell where they began, it might be exactly known when his reign will end; but for want of knowing the former, the best of calculators have failed in the latter: but seeing the time when he was made universal bishop by Phocas bids fair for the time of his open appearance, and the beginning of his reign, and of his blasphemy, which was in the year 606, to which, if we add 1260, the expiration of his reign will fall in the year 1866; so that he may have upwards of an hundred and twenty years yet to continue; but of this we cannot be certain; however, the conjecture is not improbable.