What does Mark 10:10 mean?

As they often do, once Jesus and the disciples are away from the crowd, the disciples ask for clarification (Mark 4:10, 33–34). We don't know whose "house" this is. They are either in Judea or Perea which sits on the other side of the Jordan from Judea.

Matthew reveals that the disciples overhear the Pharisees specifically ask, "Why then did Moses command one to give a certificate of divorce and send her away?" (Matthew 19:7). Either Matthew doesn't record the entire conversation, or those asking the question are missing the point. Moses never commanded that Israelites should divorce their wives. His command was that if they do divorce their wives, they give the women legal documentation to that effect. Without an official divorce, the husband could effectively banish his wife, but keep her dowry. The only time Jewish leadership commanded that men divorce their wives was as the Jews returned from exile in Babylon. As the Jews meet their fresh start, gathered again in Jerusalem, Ezra realizes that many of them married foreign women who would lead them right back into idolatry. The danger to their identity as God's chosen people was at danger, and they had to send away their wives (Ezra 10).

This causes much of the present difficulty: the disciples have completely bought into the cultural standard of divorce at will. They protest that if their choices are to remain in the marriage or divorce and remain single, it would be easier to just never marry (Matthew 19:10). The Jews, as a whole, strive to follow God's laws to the letter. They even added laws so they won't come close to breaking the commands of God (Matthew 23:4). But when it comes to marriage, they completely miss the mark. They hear Deuteronomy 24:1–4 on how to divorce their wives, but miss Malachi 2:13–16 on why divorcing their wives is a violence that causes God to reject their religious piety.