What is the biblical definition of marriage according to both the Old and New Testament?
A marriage is special covenant entered into between a man and a woman for the purpose of establishing a new family.
"For this reason a man shall leave his father and his mother, and be joined to his wife; and they shall become one flesh" (Genesis 2:24).
For a marriage to take place, the man (and the woman) separate from the family they currently are a part of and join together as husband and wife to create a new family (the on-going process of becoming one flesh).
"Yet you say, 'For what reason?' Because the LORD has been a witness between you and the wife of your youth, against whom you have dealt treacherously, though she is your companion and your wife by covenant" (Malachi 2:14).
This passage clearly states that the husband and wife relationship is established by a covenant. Covenants are a special form of vows, done before God, witnessed, recorded, and lasting for the life of the two people who enter the covenant. See Covenants and Marriage Covenants for more details.
"And He answered and said to them, "Have you not read that He who made them at the beginning 'made them male and female,' and said, 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'? So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate" (Matthew 19:4-6).
Even though it is man who enters into the covenant, it is God who actually does the joining. This implies that those wishing to enter a marriage covenant have to meet God's standards. God doesn't just "rubber stamp" whatever man decides to do. It is also for this reason that men cannot decide when to end a marriage. If a marriage ends, it must be by God's terms.
Notice that once again, marriage is defined as the union of a man and a woman. It involves only two people, one of each gender. Anything else is not a marriage.
"For the married woman is bound by law to her husband while he is living; but if her husband dies, she is released from the law concerning the husband. So then, if while her husband is living she is joined to another man, she shall be called an adulteress; but if her husband dies, she is free from the law, so that she is not an adulteress though she is joined to another man" (Romans 7:2-3).
A subtlety that many people miss is that "law" and "covenant" are actually synonyms for each other. Thus, Paul is stating that a marriage lasts as long as the law, or covenant, lasts -- which is the lifetime of the two people who entered into the covenant. Once one of the party dies, the covenant comes to an end.
Does this mean that if a couple was married by judge, or justice of the peace, it is not actually a marriage in God's eyes? Also why are gay people pushing (pushed) for it to be legal to have a ceremony done which originates from a religion which believes what they are doing is sinful? Why does it mean so much to them? One more thing. In this secular day and age what is the purpose of people who do not follow God to get married? Their view is that you don't need to be married to have sex, start a family, etc. It seems like to them marriage would be rather obsolete.
No. Paul points out in I Corinthians 7:12-15 that a Christian's marriage to a non-Christian was still a legitimate marriage. "For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband; otherwise your children would be unclean, but now they are holy" (I Corinthians 7:14). Marriage isn't made legitimate by the church or by the person who performs the ceremony. Marriage existed from the very beginning and it is God who makes marriage legitimate.
For example, a man wanting to marry a woman who is still married to another man would not have a legitimate marriage. "For the woman who has a husband is bound by the law to her husband as long as he lives. But if the husband dies, she is released from the law of her husband. So then if, while her husband lives, she marries another man, she will be called an adulteress; but if her husband dies, she is free from that law, so that she is no adulteress, though she has married another man" (Romans 7:2-3).
In answer to why there is a movement pushing for homosexual marriage, you first need to realize that the people pushing are using homosexuals as the reason, but most are not homosexuals themselves. What we are seeing is a drive to undermine Christian beliefs. Notice that all the attacks are against Christians. You don't see similar demands being made against Muslims, even though under Islamic law homosexuality carries a death penalty. Foundations, such as marriage, have been systematically attacked. You see marriage means raising children who hold onto their parents' faith. Since Christians don't go out to attack opposing groups, what has been done is to force Christians to do things that they find objectionable, and if they do decline, to use the courts to force them into submission. It really isn't much different than the days of the Roman Empire when there was an attempt to force Christians to accept idolatry and emperor worship.
What I hope we will see is the conversion of Christians from apathy and hypocrisy into staunch believers once again.
Thank you very much for answering my questions.