It is more than interesting that a true Christian "place such a big emphasis on not having sex for the first time". When Satan told Jesus to turn stones into loaves of bread, Jesus, quoting from Deuteronomy 8:3, replied: "It is written, ' Man must live, not on bread alone, but on every utterance coming forth through Jehovah 's mouth."(Matt 4:4) Every command or law that our Creator, Jehovah, has laid down, must be followed. Jesus placed even "lusting" after a woman who is not a man's wife as wrong, for he said: "You heard that it was said, ‘You must not commit adultery.’ But I say to you that everyone that keeps on looking at a woman so as to have a passion for her has already committed adultery with her in his heart."(Matt 5:27, 28)
It is within the heart that a desire begins forming and if allowed to grow, results in a sinful violation of the moral boundaries God has established. These moral boundaries are solidly placed and will not change. James wrote that "every good gift and every perfect present is from above, for it comes down from the Father of the [celestial] lights, and with him there is not a variation of the turning of the shadow."(James 1:17) James further wrote that "each (person) is tried by being drawn out and enticed by his own desire. Then the desire, when it has become fertile, gives birth to sin; in turn, sin, when it has been accomplished, brings forth death."(James 1:14, 15)
For a while a person may be able to get away with premarital sex, even during his lifetime, but unless a person comes to love God and his moral boundaries, then that person will not remain forever. John wrote to "not be loving either the world or the things in the world" and it's taste for "the desire of the flesh and the desire of the eyes and the showy display of one’s means of life, does not originate with the Father, but originates with the world."(1 John 2:15, 16)
On the other hand, at Revelation 21:6, 7, God said that "to anyone thirsting I will give from the fountain of the water of life free. Anyone conquering will inherit these things, and I shall be his God and he will be my son." Those who have fought the battle against the immoral pressures of this "world", keeping their integrity down to "the end", will be rewarded with drinking (symbolically) of the "fountain of the water of life free." Jesus obeyed his Father because he loved him.(John 14:31) And those who remain chaste, must do so because they too have "the love of the Father" within them.(1 John 2:15)
