“But from the beginning of creation, God made them male and female. For this reason a man shall leave his father and mother (and be joined to his wife), and the two shall become one flesh. So they are no longer two but one flesh. Therefore what God has joined together, no human being must separate.” (Mk 10:6-9)
Jesus’ words in today’s gospel make it clear that marriage is a sacrament in which a man and a woman are joined together permanently to make one flesh. If any of these elements are missing, then there is no marriage. He doesn’t say marriage can be between two men or two women. He also specifically states that it is permanent.
One man…one woman…forever. If anyone tries to tell you otherwise, they are wrong. If they disagree, tell them to take it up with Jesus!