Yevamot, Chapter Thirteen, Mishnah Three
This mishnah is a continuation of the previous mishnah.
Rabbi Eliezer ben Jacob says: In the case of any hindrance that was due to the husband, she is considered to be his wife;
But in the case of any hindrance that was not due to the husband she is not considered to be his wife.
There are two explanations of this mishnah in the Babylonian Talmud and of what a hindrance is. According to one explanation, if while married to this man another man offers to marry her and she refuses that marriage because she prefers her current husband, then she is considered to be his wife. This is because she has expressed her opinion that she wishes to stay in the marriage, and it is unlikely that she will later make a declaration of refusal. In such a case if she was the daughter of an Israelite married to a priest, she may eat terumah, and if she was the daughter of a priest married to an Israelite she loses her right to eat terumah. However, if the hindrance was caused by another factor, for instance the new man was not right for her, then she has not expressed a definite desire to stay with her husband and therefore she is not considered his wife.
According to the second explanation, if her husband gave her a get before she made a declaration of refusal, she is considered to have been his wife. The hindrance is the get. The consequences is that he is subsequently forbidden to marry her relatives and she his. However, if she makes a declaration of refusal, this is considered a hindrance from her. She is not considered his wife and therefore may marry his relatives, as we will learn in the upcoming mishnah.