He Divorced Her, Then Returned Her Without Witnesses
Question :
I divorced my wife one time. She did not leave the house, and we lived together and this was without reference to any of the scholars of the religion or to the Court. There were also no witnesses to our Raj'ah. Is what we did correct?
Answer:
Yes, if a man takes back his wife, either by having sexual intercourse with her or by saying: "I have taken you back," or: "I have kept you," then the Raj'ah is valid. If he had sexual intercourse with her with the intention of taking her back, the aim would be achieved by that, as long as the divorce was only one or two. However, if it was the third and final divorce, she would be forbidden to him until she had married another.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 6 Pages 69-70