References from the 11th chapter of The Revelation of St. John the Divine
3. And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth.
This verse mentions the two witnesses who will defend Jerusalem for 3 and a half years. 1260 days = 42 months = 3.5 years. Symbolically this number indicates an interrupted period of time. It may not be exactly 1260 days. As 7 is a sign of completion or perfection, half that number indicates something incomplete.
7. And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.
Eventually the two witnesses will be killed by the beast.