Mark 10:2-16 could be a tough passage to do a sermon on, where Jesus talks to the Pharisees about marriage. This is especially true, if one wanted to focus solely on Mark 10:6 as it relates to marriage; especially in light of the tension felt around the question of same-sex marriage revolving in several cases in the supreme court. My guess is that more than one preacher on Sunday will use this opportunity to go on about the "sanctity of institution of marriage between one man/one woman."
But it's important to take this in light of the context; the discussion about marriage is specifically about divorce and adultery, which Jesus goes on to explain to his disciples. It is about the long-term effect of what "God has joined," and that it is impossible for man to tear apart. In light of that, any marriage done in holy matrimony is something under the eyes of God; something for which endorsement by government makes no difference, nor the repeal of rights.
Furthermore, in the paragraph that follows, Jesus blesses little children, chastising his disciples for complaining against those that had brought them to be blessed, saying, "Let the little children come to me; do not stop them; for it is to such as these that the kingdom of God belongs." All who receive the kingdom do so as little children, one's marriage is of earth, the kingdom belongs to one's relationship with God.
