Moses often had to endure the grumbling of the people, but it must have been even more painful when they spoke against his new wife. Even his own sister and brother, Miriam and Aaron, spoke behind his back concerning the Ethiopian woman. Yet, the Lord heard them.
Miriam seems to have been the leader in the backbiting. Aaron just followed along as usual, as he had with the golden calf incident. Miriam was, after all, the older sister. The one who had watched over baby Moses as he floated down the Nile and saw him taken up by the princess of Egypt. She was a prophetess in Israel. Perhaps she had risen to a position of influence with Moses after the apparent death of his first wife. And now, with this Ethiopian woman in his life, she felt a loss of influence with Moses.
Or perhaps she was upset that he had chosen an Ethiopian to marry. The word “Ethiopian” was actually “Cushite” in the Hebrew. The land of Cush might point to the lands South of Egypt or lands in Arabia. If Miriam and Aaron were against his marrying her because of her nationality or skin color, then God’s response to their racism was soon made clear. They were against Moses because of his wife, “so the anger of the Lord was aroused against them” (Num. 12:9).
A couple of takeaways: 1) Don’t speak against God’s man. God is listening. 2) Don’t speak against someone’s marriage because of skin color. You might get leprosy and lose your skin. Miriam did.