Yevamot

regard her menstrual periods as regular  unless the recurrence had been regular three times. Nor is she released from the restrictions of an established regular period unless it has varied three  times. 'And the ox [whose owner has been] forewarned'? — As we learned: An ox is not deemed a mu'ad unless [its owner] has been forewarned three times. Our Rabbis taught: A woman who had been married to one husband and had no children and to a second husband and again had no children, may marry a third man only if he has children. If she married one who has had no children she must be divorced without receiving her kethubah. The question was raised: Where she married a third husband and bore no children, may her first two husbands reclaim [the respective amounts of her kethubah]?  Can they plead, 'It has now been proved that you were the cause',  or can she retort, 'It is only now that I have deteriorated'? — It stands to reason that she may plead, 'It is only now that I have deteriorated'. The question was raised: If she married a fourth husband and gave birth to children, may she claim her kethubah from her third husband? — We advise her: 'Your silence is better than your speech'; for  he  could tell her, 'I would not have divorced you in such circumstances'.  R. Papa demurred: Even if she keeps silence, should we remain silent? The divorce, surely,  is annulled,  and her children are bastards! In truth,  the fact is,  that it is assumed that she has now been restored to health. If the husband  pleads, 'The fault is hers'  and the wife pleads, 'The fault is his',  R. Ammi ruled: In private matrimonial affairs  the wife is believed. And what is the reason? — She is in a position to know whether emission is forceful,  but he is not in a position to know it. If the husband states that he intends taking another wife to test his potency.  R. Ammi ruled: 'He must in this case also divorce [his present wife] and pay her the amount of her kethubah; for I maintain that whosoever takes in addition to his present wife another one must divorce the former and pay her the amount of her kethubah.' Raba said: A man may marry wives in addition to his first wife; provided only that he possesses the means to maintain them.