If a man divorces his wife before consummation of the marriage, she becomes haraam for all of his offspring

No, if a man divorces a woman, she becomes haraam for all of his sons, the sons of his sons, and the sons of his daughters, because she was the wife of the father, even if he did not consummate the marriage with her, and Allah has not connected this matter to consummation of the marriage. Allah, may He be glorified and exalted, says (interpretation of the meaning): “And marry not women whom your fathers married” [an-Nisa’ 4:22]. 

Marriage to their fathers’ ex-wives is haraam for sons in all cases. “Father” in this case refers to the immediate father as well as the grandfather, i.e., the father’s father or the mother’s father. It includes all forefathers on the mother’s side and on the father’s side. Their (ex-) wives are haraam for the son to marry and he is a mahram to them because of the verse (interpretation of the meaning): “And marry not women whom your fathers married” [an-Nisa’ 4:22]. This includes the one with whom the marriage was consummated and the one with whom it was not consummated. This is a matter concerning which there is consensus among the scholars and there is no difference of opinion concerning it. 

The converse is also true: The son’s wife is also haraam for father to marry in all cases, even if the son did not consummate the marriage with her. If a man marries a woman then dies before consummating the marriage with her, or he divorces her before consummating the marriage with her, she is haraam for his father and all of his grandfathers, because Allah says (interpretation of the meaning) “the wives of your sons who (spring) from your own loins” [an-Nisa’ 4:23]; He did not say those with whom you have consummated the marriage. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him).