What is the ruling on a husband saying to his wife, "Ya Mama" (O Mama), and does this statement make his wife unlawful for him?

A man's saying to his wife: "You are my mother," or "my sister," or "O mama," does not constitute Dhihar (a pre-Islamic form of divorce by likening one's wife to an unmarriageable kin), unless he intends Dhihar by it. Most often, he says it for gentleness and respect, and thus the wife does not become forbidden to her husband thereby. Some scholars have held that it is disliked for a man to say to his wife: "O my mother," or "O my sister," but there is no basis for this dislike. The correct view is that there is no dislike in that, because "deeds are judged by intentions." As long as the husband did not intend to forbid his wife by these words, there is nothing against him.