Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh. Genesis 2:24
Marriage is the one flesh union of one man and one woman for life. This union is to be a blood covenant, a union only ended by death. Marriage establishes a new family unit.
And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female, And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh? Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder. Matthew 19:4-6
Jesus affirms this definition of marriage and shows that marriage is God-ordained and as such should not be messed with by man.
And he said unto him, I am the Lord that brought thee out of Ur of the Chaldees, to give thee this land to inherit it. And he said, Lord God, whereby shall I know that I shall inherit it? And he said unto him, Take me an heifer of three years old, and a she goat of three years old, and a ram of three years old, and a turtledove, and a young pigeon. And he took unto him all these, and divided them in the midst, and laid each piece one against another: but the birds divided he not. And when the fowls came down upon the carcases, Abram drove them away. And when the sun was going down, a deep sleep fell upon Abram; and, lo, an horror of great darkness fell upon him. And he said unto Abram, Know of a surety that thy seed shall be a stranger in a land that is not theirs, and shall serve them; and they shall afflict them four hundred years; And also that nation, whom they shall serve, will I judge: and afterward shall they come out with great substance. And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age. But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full. And it came to pass, that, when the sun went down, and it was dark, behold a smoking furnace, and a burning lamp that passed between those pieces. In the same day the Lord made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates: The Kenites, and the Kenizzites, and the Kadmonites, And the Hittites, and the Perizzites, and the Rephaims, And the Amorites, and the Canaanites, and the Girgashites, and the Jebusites. Genesis 15:7-21
For us to understand marriage, we must understand the idea of a blood covenant. In Genesis 15 we see a vivid example of God making a blood covenant with Abram. In this covenant, animals are ripped in two and God passes between the two halves. God makes an unconditional promise to Abram thus establishing the blood covenant. God is essentially telling Abram, “If I do not keep this promise you can rip me in half like these animals.” A blood covenant is an conditional promise that one makes to another that is sealed by blood.
Marriage is a blood covenant. It is an unconditional promise to remain faithful to your spouse until death.
Let your conversation be without covetousness; and be content with such things as ye have: for he hath said, I will never leave thee, nor forsake thee.
Our salvation is a blood covenant. Jesus has promised to bring us to glory. He will never leave us or forsake us as long as He lives. Jesus has sealed this promise with His own blood.
For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh. This is a great mystery: but I speak concerning Christ and the church. Ephesians 5:31-32
Marriage is to be a picture of the blood covenant between Christ and the Church.