GOD CREATED HUMANITY IN THIS WAY:
"Have you not read, that He who created them from the beginning made them male and female" (Matt. 19:4; Mark 10:6).
God said, "It is not good for the man to be alone" (Gen. 2:18a). Any man; every man; all encompassed in Adam, our head and representative. God then continued by saying, "I will make a helper suitable for him" (Gen. 2:18b). The phrase "meet for" (KJV) in Genesis 2:18 comes from two Hebrew words. The first, #5048, is a preposition indicating before, in front of, opposite. The second, #3509.1, is a marker of comparison: as, like; a marker of similarity or correspondence. The phrase "meet for" in the Hebrew indicates something that is both similar yet different; something that was similar to Adam yet completely different from him. Not a mirrored image, which is entirely the same and identical. As other translations render it (more accurately, I might add), this is what was "suitable" for not only Adam but for every man—woman. Every animal in the animal kingdom had its suitable pair, something that was similar but different—its female counterpart. The similarity was in its kind; the difference was in its make up. Adam saw that every animal had its appropriate pair while he did not. Thus, God said "It is not good for man to be alone." In creating the "suitable" helper for Adam, He created woman. Woman is similar to Adam, being of the same species; but different from him, being a woman and having womanly parts rather than manly parts. This difference would be key to the mandate that God would give to the two of them, which is the same mandate given to all mankind—"Be fruitful and multiply" (Gen. 1:28).
GOD INTENDED HUMAN RELATIONSHIPS TO FUNCTION LIKE THIS:
"For this reason a man shall leave his father and his mother, and be joined to his wife; and they shall become one flesh" (Gen. 2:24; Matt. 19:5; Mark 10:7-8).
The creation account gives a very clear picture—a standard—of God's intention for all human relationships. The only standard for sexual expression you will find consistently praised in both Testaments is that of heterosexual monogamy. Throughout the entire Bible, only that standard is upheld. Both Jesus and the Apostle Paul upheld the standard of heterosexuality. If I uphold the life of a child in the womb, I am necessarily opposed to abortion. Likewise, Scripture, Jesus, and the Apostle Paul, while upholding the standard of heterosexuality, are necessarily opposed to homosexuality (and every other sexual deviation). The statement encompasses every man; all men: "For this reason a man [any man, every man, all men] shall leave his father and his mother, and be joined to his wife; and they shall become one flesh" (Gen. 2:24). Jesus made the point of directing his listeners back to the beginning, the creation of humanity, which tells us everything we need to know about God's design, plan, and intention for human relationships. Anything outside of this union—one man and one woman—is a perverse, abnormal, unnatural, abominable sexual deviation.
GOD GAVE HUMANITY THIS MANDATE:
"Be fruitful and multiply" (Gen. 1:22).
Man and woman were perfectly designed for each other; both for pleasure and for procreation: "Be fruitful and multiply" (Gen. 1:28). The genital parts of both man and woman were designed differently yet complimentary—they fit together perfectly. They are, by design, perfectly fit for each other; perfectly matched. Like a light bulb and a socket, a plug and an outlet, a bolt and a nut, male and female genitalia were perfectly designed for complimentary union. This union of man and woman is the only means with which to create progeny and carry on one's family name as well as the human race. Humanity would die outside of this union and this mandate. Every living creature that God created, those in the water, those in the air, and those on the land, were all given the mandate to "be fruitful and multiply." They could not fill the waters and the air and the land otherwise. Humanity was given the same mandate, which is an expectancy of how God intended human relationships to function, the standard upheld by both Jesus and the Apostle Paul.