Mar 10:3 What did Moses command you?
Note that Christ describes the commandments as Mose's laws. Christ refers to the commandments as specific to Moses, while "the law" (nomos) come from the entire tradition of Jewish history (Mat 11:13). The law is bigger than the commandments, but the commandments are the basis of the law. Both are permanent fixture in human history (Mat 5:18).
For Christ, this is where the discussion of the laws of the universe (the universal rule or kingdom of heaven) begins. The law started with Moses explained certain aspects of how the world works. Christ agrees with all of that explanation and only seeks to extend it and to encourage all of us to extend it.
"What" is from tis, which can mean "someone," "any one," "everyone," "many a one," "whoever," and so on. In a question, it can mean "who," or "what."
"Command" is from entellô (entello), which means "to enjoin," and "to command."