The book of Revelation refers to 144,000 servants of God who will be sealed in two different places. I have heard that the Jehovah's Witnesses often refer to this number.
Who, exactly, do the Jehovah's Witnesses believe these people to be? Are they members of the Jehovah's Witnesses who lived in the past, who are living in the present, or who will live in the future? Or are they male Jewish virgins, as the text suggests, who will live at some point in the future? (male, virgins - "who have not defiled themselves with women", Jewish - "from every tribe of the sons of Israel")
After this I saw four angels standing at the four corners of the earth, holding back the four winds of the earth, that no wind might blow on earth or sea or against any tree. Then I saw another angel ascending from the rising of the sun, with the seal of the living God, and he called with a loud voice to the four angels who had been given power to harm earth and sea, saying, “Do not harm the earth or the sea or the trees, until we have sealed the servants of our God on their foreheads.”
And I heard the number of the sealed, 144,000, sealed from every tribe of the sons of Israel: 12,000 from the tribe of Judah were sealed, 12,000 from the tribe of Reuben, 12,000 from the tribe of Gad, 12,000 from the tribe of Asher, 12,000 from the tribe of Naphtali, 12,000 from the tribe of Manasseh, 12,000 from the tribe of Simeon, 12,000 from the tribe of Levi, 12,000 from the tribe of Issachar, 12,000 from the tribe of Zebulun, 12,000 from the tribe of Joseph, 12,000 from the tribe of Benjamin were sealed. Revelation 7:1-8 ESV
Then I looked, and behold, on Mount Zion stood the Lamb, and with him 144,000 who had his name and his Father's name written on their foreheads. And I heard a voice from heaven like the roar of many waters and like the sound of loud thunder. The voice I heard was like the sound of harpists playing on their harps, and they were singing a new song before the throne and before the four living creatures and before the elders. No one could learn that song except the 144,000 who had been redeemed from the earth. It is these who have not defiled themselves with women, for they are virgins. It is these who follow the Lamb wherever he goes. These have been redeemed from mankind as firstfruits for God and the Lamb, and in their mouth no lie was found, for they are blameless. Revelation 14:1-5 ESV