3. I will give power--There is no "power" in the Greek, so that "give" must mean "give commission," or some such word.
      my two witnesses--Greek, "the two witnesses of me." The article implies that the two were well known at least to John.
      prophesy--preach under the inspiration of the Spirit, denouncing judgments against the apostate. They are described by symbol as "the two olive trees" and "the two candlesticks," or lamp-stands, "standing before the God of the earth." The reference is to Zec 4:3, 12, where two individuals are meant, Joshua and Zerubbabel, who ministered to the Jewish Church, just as the two olive trees emptied the oil out of themselves into the bowl of the candlestick. So in the final apostasy God will raise up two inspired witnesses to minister encouragement to the afflicted, though sealed, remnant. As two candlesticks are mentioned in Re 11:4, but only one in Zec 4:2, I think the twofold Church, Jewish and Gentile, may be meant by the two candlesticks represented by the two witnesses: just as in Re 7:1-8 there are described first the sealed of Israel, then those of all nations. But see on Re 11:4. The actions of the two witnesses are just those of Moses when witnessing for God against Pharaoh (the type of Antichrist, the last and greatest foe of Israel), turning the waters into blood, and smiting with plagues; and of Elijah (the witness for God in an almost universal apostasy of Israel, a remnant of seven thousand, however, being left, as the 144,000 sealed, Re 7:1-8) causing fire by his word to devour the enemy, and shutting heaven, so that it rained not for three years and six months, the very time (1260 days) during which the two witnesses prophesy. Moreover, the words "witness" and "prophesy" are usually applied to individuals, not to abstractions (compare Ps 52:8). DE BURGH thinks Elijah and Moses will again appear, as Mal 4:5, 6 seems to imply (compare Mt 17:11; Ac 3:21). Moses and Elijah appeared with Christ at the Transfiguration, which foreshadowed His coming millennial kingdom. As to Moses, compare De 34:5, 6; Jude 9. Elias' genius and mode of procedure bears the same relation to the "second" coming of Christ, that John the Baptist's did to the first coming [BENGEL]. Many of the early Church thought the two witnesses to be Enoch and Elijah. This would avoid the difficulty of the dying a second time, for these have never yet died; but, perhaps, shall be the witnesses slain. Still, the turning the water to blood, and the plagues (Re 11:6), apply best to "Moses (compare Re 15:3, the song of Moses"). The transfiguration glory of Moses and Elias was not their permanent resurrection-state, which shall not be till Christ shall come to glorify His saints, for He has precedence before all in rising. An objection to this interpretation is that those blessed departed servants of God would have to submit to death (Re 11:7, 8), and this in Moses' case a second time, which Heb 9:27 denies. See on Zec 4:11, 12, on the two witnesses as answering to "the two olive trees." The two olive trees are channels of the oil feeding the Church, and symbols of peace. The Holy Spirit is the oil in them. Christ's witnesses, in remarkable times of the Church's history, have generally appeared in pairs: as Moses and Aaron, the inspired civil and religious authorities; Caleb and Joshua; Ezekiel the priest and Daniel the prophet; Zerubbabel and Joshua.
      in sackcloth--the garment of prophets, especially when calling people to mortification of their sins, and to repentance. Their very exterior aspect accorded with their teachings: so Elijah, and John who came in His spirit and power. The sackcloth of the witnesses is a catch word linking this episode under the sixth trumpet, with the sun black as sackcloth (in righteous retribution on the apostates who rejected God's witnesses) under the sixth seal (Re 6:12).

JFB.