Does the act of sex constitute marriage in God's eyes?

In another viewpoint, Tony Evans, calls sex outside of marriage, a "non-marriage marriage".

Sex was designed & intended to create a lifelong bond between the man & woman. He shares the analogy of sex being like gluing two boards together with extremely strong glue. Sex without the commitment of marriage, when the two part the boards actually rip apart leaving parts of each board glued to the other board. So sex outside of marriage has some of the characteristics of marriage, one flesh in a sense, but not the lifelong commitment or the maintainenance of a lifelong relationship.

I don't know exactly which sermon he said this in, but this is a good starting point

Also, OnePlace has some of his recent sermons.

Considering both biblical and secular traditions of marriage, what seems to be required for a valid marriage is public acknowledgement and acceptance of the relationship with sex being something that traditionally follows the public recognition.

The New Testament demonstrates strong parallels between marriage and baptism. As a Baptist, if you're a believer you're expected to make a public declaration (Mat 10:32-33, Luk 12:8-9) of your faith through baptism (Mar 16:16). In marriage you make a public declaration of your commitment to your spouse.

Jesus' first recorded miracle was at a wedding feast, and in one of his parables he spoke of the foolish virgins waiting for the bridegroom. As someone has already mentioned he spoke of the Samaritan woman as not being married to the man she was currently with. There's plenty of scripture that compares marriage with the church's and individual's relationship with Christ, and nowhere is the suggestion that either is a hidden thing kept out of public knowledge.

I'd say sex without public recognition of a relationship is not marriage, but on the other hand public recognition doesn't need to be as elaborate as many people make it.

While there is mention in the Bible of abiding by local laws (eg render under Caesar what is Caesar's), in many countries there's no law that states that you are required to hold a marriage certificate to be accepted as a couple. It certainly provides legal recognition, but comparing a registry office marriage with no friends or family present to a celebration with them present, but with no official paperwork, I think in some ways the latter might actually represent a more authentic marriage in the eyes of God, unless there were some reason that family would not support the marriage, (however from a Christian perspective even if blood relatives don't support the marriage there's still the church family).

Jesus was extremely clear that divorce for any reason other than sexual immorality (Mat 5:32) on the part of a spouse is adultery, so to suggest sex with good intent is "marriage in God's eyes", it would also have to follow that failure to follow up on that good intent makes both adulterers.

Paul speaks of marriage to avoid inflamed passions leading to sin (1 Cor. 7), but he also urges restraint even in marriage, as to him, Christ should be the supreme centre of our attention. I don't think Paul was suggesting married people should not enjoy sex, but more that sex should not be such a preoccupation that there's no time left for Christ.

It is strange to me that we talk about the 'sacrament of marriage'. I suppose that works for a Roman Catholic... however I don't find any description in Scripture that tells me exactly what constitutes marriage. There is no specific ceremony given.

We see however in Genesis 4:1 (Now Adam knew Eve his wife, and she conceived and bore Cain, and said, “I have acquired a man from the Lord.”) that Eve was already Adam's wife before this act. Had the previously consummated their marriage? Even as far back as Genesis 2:21-24 Eve appears to be called Adam's wife, I would assume here before any consummation of anything.

Another example can be found in Genesis 24:67 (Then Isaac brought her into his mother Sarah’s tent; and he took Rebekah and she became his wife...) This passage seems to support the view that Sex = marriage, however I do not agree that it does.

My thought is that marriage has more to do with our intentions before God to be joined as one flesh permanently and fornication has to do with not having that intention. So that sex with no intention to become married does not equate to marriage, but sex with intention to be one flesh does equal marriage in God's eyes.

I don't know any place in the Bible that actually defines marriage, but there are some clues, like:

Gen 34:1-4 Shechem has sexual relations with Dinah, and then AFTER doing this, says he wants to marry her.

As Cwallenpoole points out, if sex equaled marriage, then there could be no such thing as adultery or premarital sex by definition.

I don't know any place in the Bible that refers to two people who have a one-night stand as "married". The Bible describes plenty of such activity, so it's not for lack of an example.

Gen 2:24 says a man will "leave his father and mother and be joined to his wife". The implication is that marriage is more than just sex: it involves a long-term commitment.

In Matt 19:3-12, Jesus says that divorce is allowed only in very limited circumstances. So marriage is a life-time commitment.

I think the reasonable conclusion is that it includes a life-time commitment to live with the other person and to limit one's sexual activity to one's husband or wife. (Multiple wives was apparently permitted or at least tolerated. I don't know any references to multiple husbands in the Bible.)

The Bible doesn't require any particular ceremoney or ritual to become married. Whether God would accept two people just saying, "Hey, let's declare ourselves married", I don't know. If they were stranded on an island with no pastor or priest around to perform a marriage ceremony, I think God would accept that. If they refuse to have a ceremony because they don't want to make a formal commitment, I don't think God would accept that.

The words of Jesus answer this:

The fact is, you have had five husbands, and the man you now have is not your husband. What you have just said is quite true.

John 4:18

Clearly Jesus did not associate the Samaritans woman's relationship with marriage.

Jesus does not seem to consider merely being with a man to make him your husband.

John 4:16-19 (DRA)
¹⁶ Jesus saith to her: Go, call thy husband, and come hither. 17 The woman answered, and said: I have no husband. Jesus said to her: Thou hast said well, I have no husband:
    ¹⁸ For thou hast had five husbands: and he whom thou now hast, is not thy husband. This thou hast said truly.
    ¹⁹ The woman saith to him: Sir, I perceive that thou art a prophet.
   

However, another reading this verse will lead you to one amazing conclusion which was pointed out by my Bishop in Madison, Wisconsin (I don't know where he got it from). He said that to the Jews, the number 7 was a perfect number. Once it reached the 7th thing, it wasn't going to get any better. So this lady had 5 husbands, but 7 lovers. The 7th being Jesus, the penultimate lover of her soul.

Not that you care, but to a Catholic, we might say, if she gave up her old ways, that she was married to Christ. We're pretty particular about what conjugal relations make up marriage, but very liberal about what spiritual relations constitute marriage.

Marriage is that which makes husband and wife, mother and father.

Short and sweet answer: No, otherwise fornication would be impossible.