And those who dwell on the earth
The phrase "who dwell on the earth" is used in particular for non-believers: Revelation 3:10; Revelation 6:9-10; Revelation 8:13; Revelation 13:8; Revelation 14:6-7; and Revelation 17:8.
will REJOICE over them and make MERRY; and they
Why the rejoicing?
Most likely, Christmas was a celebration without even the possibility of remembering Christ's birth. The antichrist will have decreed it so. These two witnesses had reminded the world WHY they had sent gifts.
will SEND GIFTS to one another, because these two prophets TORMENTED those who dwell on the earth.
This celebration coincides with the Festival of Purim (Esther 9:20-28), the Jewish gift-giving festival. Since the festival is held on the 13th day of Adar month (Jewish calendar), most likely these two witnesses are killed on this day. Watch for it. Note: the Desert Storm Persian Gulf conflict concluded on the Festival of Purim. Coincidence or ???
The two witnesses, as witnesses usually do, cause a study in contrasts. To believers, they would have brought joyous testimony. To non-believers, they will bring terrible torment.