Christian beliefs about marriage:
1)important sacrament: "In the presence of God, I take this vow" (Galatians 6:9)- God is involved in the ceremony, reinstates marriage being sacred and binding ("What God has joined together let no-one separate", Mark 10)
2) Marriage is a gift from God, it's a part of God's plan for men and women to live together
"Is it not good for men to be alone, I will make a helper for him" (Genesis 2) --> links to "Marriage was established by God when he created humans" (Mark 10) and gender roles
3) provides a stable environment for children