The first use of the Greek term "tribulation" is seen when Jesus teaches the Parable of the Sower.
The one on whom seed was sown on the rocky places, this is the man who hears the word and immediately
receives it with joy; yet he has no firm root in himself, but is only temporary, and when affliction or persecution arises
because of the word, immediately he falls away. (Matt 13:20-21;
Mark 4:16-17)
Here Jesus indicates that "affliction" or "tribulation" describes the persecution of one's faith in God, and
He exclusively applies the term to Believers; thus, limiting its use to the persecution of one's faith. This makes a distinction
from other causes of persecution (i.e. racism, socio-economic class, etc.).
When studying Revelation, there are 3 instances when human beings are mentioned in the Temple of God. In each instance, these
human beings appear to be those who were martyred during the Great Tribulation, which were either Believers who died for their
faith or the 144,000 bond servants (Rev 6:9-11; Rev 7:13-15;
14:1-3).
It is significant to note that those Believers who were martyred for their faith before Jesus Christ returns reside underneath
the altar in the Temple of God and emerge later, when Jesus breaks the seals, to receive their white robe and serve God Himself.
When the Lamb broke the fifth seal, I saw underneath the altar the souls of those who had been slain
because of the word of God, and because of the testimony which they had maintained; and they cried out with a loud voice,
saying, "How long, O Lord, holy and true, will You refrain from judging and avenging our blood on those who dwell on the earth?"
And there was given to each of them a white robe; and they were told that they should rest for a little while longer, until the
number of their fellow servants and their brethren who were to be killed even as they had been, would be completed also.
(Rev 6:9-11)
Then one of the elders answered, saying to me, "These who are clothed in the white robes, who are they,
and where have they come from?" I said to him, "My lord, you know." And he said to me, "These are the ones who come out of the
great tribulation, and they have washed their robes and made them white in the blood of the Lamb. For this reason, they are
before the throne of God; and they serve Him day and night in His temple; and He who sits on the throne will spread His tabernacle
over them. (Rev 7:13-15)
Then I looked, and behold, the Lamb was standing on Mount Zion, and with Him one hundred and
forty-four thousand, having His name and the name of His Father written on their foreheads. And I heard a voice from heaven,
like the sound of many waters and like the sound of loud thunder, and the voice which I heard was like the sound of harpists
playing on their harps. And they sang a new song before the throne and before the four living creatures and the elders; and no
one could learn the song except the one hundred and forty-four thousand who had been purchased from the earth.
(Rev 14:1-3)