The book of Revelation is written in apocalyptic (symbolic) language as I previously explained, this is what the two witnesses mean mentioned in Revelation 11:3-14. Throughout the Bible, the number two is the number symbolizing strength. Jesus sent the 70 out two by two. The Jewish law in the Old Testament required two witnesses before someone was convicted (Deuteronomy 17:6). Moses and Elijah (two) appeared with Jesus on the Mount of Transfiguration.
These two witnesses in Revelation symbolize the true church and refer to the missionary and witnessing activity of the church. The church is called to testify during the one thousand two hundred and sixty days (1,260 - three and a half years). The three and a half years are years of tribulation. Jesus said, "In the world you will have tribulation" (John 16:33). Revelation was written to Christians experiencing great tribulation and persecution. I don't think we are going to have a Great Tribulation at the end of time like the pre-milleniallists believe and teach. I believe Revelation and Christ teaches that we live in great tribulation then and now.
These two witnesses (the church) are two testify, proclaim, or prophesy (which means forth-telling - not future telling) God's message of salvation and judgment. The two witnesses (the church) will tell the message in the midst of grief and trouble to them while being trampled over by the world. In heaven, the witnesses wear white robes of victory. On earth, they wear sackcloth which is the symbol of grief and mourning. Like Jesus who mourned over Jerusalem (Matthew 23:37). Truely, the condition of this world and our country causes us to mourn and wear sackcloth and ashes.
John, the Revelator, is reminding us (the church) symbolized by the two witnesses that we are channels of divine strength flowing to His chosen people, the church. In Revelation 11:5, the fire coming out of their mouths is not literal - fire is always the symbol for the jugment of God. the message the witnesses (the true church proclaims) judges the world and destroys the power of the devil every time a person receives Christ. 1 Corinthians 6:2 affirms, "Do you not know that the saints (the true church) will judge the world?" (NIV). And, that is what the two witnesses are doing - judging the world because the two witnesses are the true church. Those who injure God's witnesses (the true church) will suffer for their folly.
In Revelation 11:7, there is a parallel to the finished work of Christ and the finished work of the witnesses (the church). The witnesses were persecued and killed by the Beast (the devil working in the world) and the power of evil seemed to prevail just as it seemed to prevail when Jesus died. Righteousness and God's way seemed to be doomed. But Christ arose! And the two witnesses (the true church) are secure, indestructible, and invincible until their full work is accomplished.
This truth is played out looking back in history. The church in China was severely persecuted and pastors and Christians suffered and were executed. The same was true in Communist Russia. But, we see the church continuing, strong, victorious because their work is not finished and will not be finished until the Lord returns.
The great message of Revelation is the victory of Christ and His church. That message was of great hope and reality to the Christians John wrote to in 100AD and is true today to Christians who suffer and die for their faith like they are doing in Iran and Iraq and many other places. The message of Revelation is truth and encouragement for us today and is not about giving details of the "end" time like the pre-millenialists interpret, believe, and teach.