Seven days whenever seen signifies something. And after God created everything and He saw that it was Good and He rested on the seventh day. After seven days Miriam was brought back when God saw that she was holy and good to be in the mist of the other good ones.

This is a lesson to all , God wants us to be holy so that He can defend us even in the face of battle or in the secret places we can't get to. Moses was holy and meek and that was why God was able to defend Him.

God can never be like men who despise other ethnics, God is God and no man knows what is best for them except God. All ethnics, tribe, country are all from God.