After being married for teyears I think I have a better idea why marriage is necessary for a relationship instead of cohabiting together. Marriage is a promise you make between your self and your spouse united in God, to stay together no matter what. God uses marriage to grow and change you into the person He wants you to be. Inside of marriage physical intimacy is a great tool God made to grow us closer together as husband and wife. Outside of the safety of marriage sex is just an obstacle to trip over. It doesn’t help you but hurts you. I have been on both sides of the fence and I am grateful to have passed to the better side. “.. And I pray that you, being rooted and established in love, may have power, together with all the Lord’s holy people, to grasp how wide and long and high and deep is the love of Christ, and to know this love that surpasses knowledge—that you may be filled to the measure of all the fullness of God.” (Eph 3:17-19)