Revelation 7
1 And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.
2 And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea,
3 Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads.
4 And I heard the number of them which were sealed: and there were sealed an hundred and forty and four thousand of all the tribes of the children of Israel.
1 And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.
2 And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea,
3 Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads.
4 And I heard the number of them which were sealed: and there were sealed an hundred and forty and four thousand of all the tribes of the children of Israel.
However…. Revelation 14 is in Heaven, not on the earth. See verse 3 below. These 144,000, are these the martyrs who were killed? In Revelation chapter seven they are alive on Earth, but in chapter fourteen they are in Heaven, and Christ doesn't arrive on Earth for His Second Advent until chapter nineteen. Ergo, they died; they were "redeemed from the Earth" through death. Observe:
Revelation 14:1-3
14 And I looked, and, lo, a Lamb stood on the mount Sion, and with him an hundred forty and four thousand, having his Father's name written in their foreheads.
2 And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and I heard the voice of harpers harping with their harps:
3 And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred and forty and four thousand, which were redeemed from[apo, Grk. #575] the earth. KJV
from: Greek word #575 apo (apo'); a primary particle; "off," i.e.away (from something near), in various senses (of place, time, or relation; literal or figurative): KJV - (X here-) after, ago, at, because of, before, by (the space of), for (-th), from, in, (out) of, off, (up-) on (-ce), since, with. In composition (as a prefix) it usually denotes separation, departure, cessation, completion, reversal, etc.