The Gauge by Which the Validity of Ar-Raj'ah is Measured in the Waiting Period, Not the Time

Question :

I divorced my wife and after three months and twenty days, I took her back. After her return to me, she became pregnant and delivered a child. What atonement is incumbent upon me?

Answer:

There is no atonement for this action, but it must be ascertained whether she was taken back before the completion of her waiting period, in which case, it is valid. This is because three months and ten days or more might pass. for a woman and she might still be in her waiting period. The waiting period of a woman is one in which she has three menstrual periods. Three menstrual periods might not come in three months, since there are some women who only menstruate every two months, so such a woman's waiting period would not be complete until six months had passed.

However, if she was taken back after the completion of her waiting period, that is, after she had menstruated three times, then taking her back is not valid. Because when a woman's waiting period is over, she becomes unrelated to her husband and she is not permissible for him, except with a new contract. So if this is the case, meaning, her waiting period ended before he took her back, then he must now make a new contract for her.

And the important thing is that if you took her back after three months and ten days, before she had menstruated three times. Then she is now your wife and taking her back was valid. But if you took her back after she completed her waiting period, then taking her back was not valid, the woman is not your wife, and you must make a new contract for her, with witnesses, a dowry and her guardian.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 6 Page 71