How do we know the doctrine of marriage being for life is true?

Jesus Christ made clear in Matthew 19 that marriage is intended to be a lifelong union. He cites the creation account, emphasizing that God created man and woman for each other, establishing a model for marriage. The concept that a man shall leave his father and mother and be joined to his wife indicates a divine plan for marital unity. Furthermore, Ephesians 5 draws a parallel between marriage and the covenant relationship between Christ and His Church, further solidifying the belief that marriage is designed to be a permanent commitment, just as the union between Christ and His believers is eternal.