It appears from the following scriptures that God considers the commitment of betrothal, (or engagement to be married) just as indicative of marriage as the act of intercourse. In the Old Testament Israel, if a man forcibly had intercourse with a virgin and they were found out, then he had to keep her as his wife and pay her father money. However, I find it interesting that it says ‘if they are found out’. What then if they were not discovered. Also of note is that, as djanakes mentioned, feigning virginity and getting married or having sex outside of marriage while still living with her father was deserving of death for a woman in Israel.
Deuteronomy 22:13-30 -
13“If any man takes a wife, and goes in to her, and detests her, 14“and charges her with shameful conduct, and brings a bad name on her, and says, ‘I took this woman, and when I came to her I found she was not a virgin,’ 15“then the father and mother of the young woman shall take and bring out the evidence of the young woman’s virginity to the elders of the city at the gate. 16“And the young woman’s father shall say to the elders, ‘I gave my daughter to this man as wife, and he detests her. 17‘Now he has charged her with shameful conduct, saying, “I found your daughter was not a virgin,” and yet these are the evidences of my daughter’s virginity.’ And they shall spread the cloth before the elders of the city. 18“Then the elders of that city shall take that man and punish him; 19“and they shall fine him one hundred shekels of silver and give them to the father of the young woman, because he has brought a bad name on a virgin of Israel. And she shall be his wife; he cannot divorce her all his days. 20“But if the thing is true, and evidences of virginity are not found for the young woman, 21“then they shall bring out the young woman to the door of her father’s house, and the men of her city shall stone her to death with stones, because she has done a disgraceful thing in Israel, to play the harlot in her father’s house. So you shall put away the evil from among you.
22“If a man is found lying with a woman married to a husband, then both of them shall die—the man that lay with the woman, and the woman; so you shall put away the evil from Israel.
23“If a young woman who is a virgin is betrothed to a husband, and a man finds her in the city and lies with her, 24“then you shall bring them both out to the gate of that city, and you shall stone them to death with stones, the young woman because she did not cry out in the city, and the man because he humbled his neighbor’s wife; so you shall put away the evil from among you.
25“But if a man finds a betrothed young woman in the countryside, and the man forces her and lies with her, then only the man who lay with her shall die. 26“But you shall do nothing to the young woman; there is in the young woman no sin deserving of death, for just as when a man rises against his neighbor and kills him, even so is this matter. 27“For he found her in the countryside, and the betrothed young woman cried out, but there was no one to save her.
28“If a man finds a young woman who is a virgin, who is not betrothed, and he seizes her and lies with her, and they are found out, 29“then the man who lay with her shall give to the young woman’s father fifty shekels of silver, and she shall be his wife because he has humbled her; he shall not be permitted to divorce her all his days.
30“A man shall not take his father’s wife, nor uncover his father’s bed.
Here is a scripture which we are all aware of in which Joseph is betrothed to Mary, but they have not had intercourse, (indeed they did not have intercourse until after Jesus was born) but it says that they are husband and wife.
Matthew 1:18-25 -
18Now the birth of Jesus Christ was as follows: After His mother Mary was betrothed to Joseph, before they came together, she was found with child of the Holy Spirit. 19Then Joseph her husband, being a just man, and not wanting to make her a public example, was minded to put her away secretly. 20But while he thought about these things, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not be afraid to take to you Mary your wife, for that which is conceived in her is of the Holy Spirit. 21“And she will bring forth a Son, and you shall call His name JESUS, for He will save His people from their sins.” 22So all this was done that it might be fulfilled which was spoken by the Lord through the prophet, saying: 23“Behold, the virgin shall be with child, and bear a Son, and they shall call His name Immanuel,” which is translated, “God with us.” 24Then Joseph, being aroused from sleep, did as the angel of the Lord commanded him and took to him his wife, 25and did not know her till she had brought forth her firstborn Son. And he called His name JESUS.
Just as in secular law a verbal contract is binding, I believe that if two people enter into a verbal contract before God and agree that they are married, then He will honor that as a marriage whether or not they have intercourse.
Intercourse is symbolic of Christ coming for His church. That is why it is so sacred and to be confined to marriage. This is also why the devil so wants to pervert it. However, we are already ‘joined’ to Jesus in Spirit and are already members of His body through our verbal ‘commitment’ as evidenced by our lifestyle of coming out of the world, even though the Head, (Jesus) has not yet come to be physically ‘joined’ with the body/bride, (Ephesians chapters 4-5). If we partake in the ways of the world, especially become too interested in material things and money, then God considers that adultery, (James 4:1-5). If we come out of the world, then we become like spiritual virgins. Though we are only 'betrothed' to Jesus, God still considers us married to Him, (II Corinthians 11:2).
II Corinthians 11:1-5 -
1Oh, that you would bear with me in a little folly—and indeed you do bear with me. 2For I am jealous for you with godly jealousy. For I have betrothed you to one husband, that I may present you as a chaste virgin to Christ. 3But I fear, lest somehow, as the serpent deceived Eve by his craftiness, so your minds may be corrupted from the simplicity that is in Christ. 4For if he who comes preaches another Jesus whom we have not preached, or if you receive a different spirit which you have not received, or a different gospel which you have not accepted—you may well put up with it!
The Holy Bible, New King James Version, (Nashville, Tennessee: Thomas Nelson, Inc.) 1982.
When Jesus comes back and we are physically 'joined' to Him there will be a wedding feast and we will actually ‘consummate’ the marriage. However, even though we are now only ‘betrothed’ to Jesus, God considers us to be 'married', just like Jesus said that He had ‘finished’ the work that God had sent Him here to do, even before He went to the cross, (John 17:4). He was speaking by the Spirit those things that were not yet in the natural. It is the intent or the 'spirit' of the law, (i.e., the actions that result from the attitude) that matters most to God, not the letter. That is why Jesus said, (in what I call the path to perfection - Matthew chapters 5-7) that one can commit adultery in the heart.
Matthew 5:27-28 -
27“You have heard that it was said to those of old, ‘You shall not commit adultery.’ 28“But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.
The Holy Bible, New King James Version, (Nashville, Tennessee: Thomas Nelson, Inc.) 1982.
Marriage is a heart issue as well. Intercourse is a symbolic physical act to confirm the heart intent of unity, (both between human and human and God and humans). As such, I believe intercourse, (especially with Christians) is neither necessary nor sufficient to confirm marriage, depending on the case.
Be blessed,
Dr. Ray