Matrimony is a sacrament instituted by God through which a man and a woman enter into a lifetime agreement by vows (oaths) made to each other in the presence of God.

The husband and wife agree to become one flesh with each other exclusively that they might be joined together in a physical and spiritual union that can only be severed by death.  "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 conceerning Christ and the church.  nevertheless let every one of you in particular so love his wife even as himself: and the wife see that she reverence her husband."  Ephesians 5:31-33

Unless the husband and wife are joined in spirit, they miss the plan and purpose of God for matrimony . . . to make their love a reflection of the love of Christ for His bride, the Church.  "Wherefore they are no more twain, but one flesh.  What therefore God hath joined together, let no man put asunder.  Matthew 19:6.