the general import of His saying, Exalted is He: “And lawful to you are all beyond these.” [Quran 4:24] There is no unmarriageable kinship between this man and this woman; therefore, if the conditions are fulfilled, the marriage contract is valid.
Some scholars say that she is never lawful for him. This is narrated from the Commander of the Believers, Umar (1), as a punishment for what he did in marrying her while she was observing her waiting period. Allah, Exalted is He, says: “Do not resolve upon a marriage contract until the prescribed term is reached.” [Quran 2:235] The juristic maxim recognized by the scholars of fiqh is: “Whoever seeks something before its proper time is punished by being deprived of it.” This man hastened to marry this woman while she was observing her waiting period, so he is punished by being deprived of her.
Some scholars say that she becomes lawful for him once she begins her waiting period for him. Thus, when the waiting period for the first husband ends, she becomes lawful for the second, because the waiting period is for him and the child, if any, would be his; therefore, she becomes lawful for him. It has previously been mentioned, in the discussion of women prohibited in marriage, that a woman observing a waiting period from a man, or undergoing an istibrāʾ period on account of him, is lawful to him if her waiting period results from intercourse for which the child's lineage is attributed to the man who had intercourse with her.
In my view, this matter should be referred to the judge’s discretionary judgment, since it is narrated from the Commander of the Believers, Umar (1), who was known for his sound governance. If the judge considers it appropriate to prohibit her from him permanently, as a punishment for him and a deterrent to others, there is nothing wrong with that—for instance, where he deliberately committed the prohibited act by marrying her during her waiting period. This falls under discretionary punishment, which may consist of destroying or confiscating what a person values, such as financial penalties. Similarly, Umar (1) imposed the threefold divorce upon those who pronounced it three times, treating it as binding upon them (2).