The first rapture before the Tribulation is exclusive to Christians who are overcomers. Not all Christians are overcomers for many, actually most, still lie on a bed of fornication. They are not ready to be received up. Luke 21.36, Rev. 3.10 and Matt. 24.40-42 tell us who is raptured at the 1st rapture (according to readiness): "Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man ... Because thou didst keep the word of my patience [do all Christians keep the word of His patience?], I also will keep thee from the hour of trial [of the Tribulation itself], that hour which is to come upon the whole world, to try them that dwell upon the earth [even believers] ... Then shall two men be in the field; one is taken [better to be taken than left], and one is left: two women shall be grinding at the mill; one is taken, and one is left. Watch therefore: for ye know not on what day your Lord cometh." Both the taken and left refer to believers. Why then are some not raptured [taken] beforehand? It is conditional. Are all Christians watchful, prayerful? Of course not. "Remember therefore how thou hast received and didst hear; and keep it, and repent. If therefore thou shalt not watch, I will come as a thief, and thou shalt not know what hour I will come upon thee" (Rev. 3.3). You can know when Jesus returns if you are watchful, and it will be revealed to you; just as I know when Jesus returns, so you may know also if you are watchful, prayerful and keep the word of His patience. Praise the Lord! Amen.