Divorce is according to the intention of the one divorcing

It is narrated from Sayyiduna Rukanah bin Abd Yazid (may Allah be pleased with him) that in the blessed time of the Messenger of Allah (peace and blessings be upon him) he divorced his wife with the word «al-battah» (that is, decisively and irrevocably). He relates: I asked the Prophet (peace and blessings be upon him) about this, and he (peace and blessings be upon him) asked: "What did you intend by it?" He said: I intended only one divorce. He (peace and blessings be upon him) said: "By Allah (did you mean only one)?" He said: Yes, by Allah! He (peace and blessings be upon him) said: "Then it is what you intended."
Although the two Shaykhs turned away from the narration of al-Zubayr bin Sa'id al-Hashimi in their two Sahihs, this hadith has a corroborating narration (mutabi') from the family of Rukanah bin Abd Yazid, by which the hadith is established as sahih.

It is narrated from Nafi' bin Ujayr bin Abd Yazid that Sayyiduna Rukanah bin Abd Yazid (may Allah be pleased with him) divorced his wife Suhaymah with the word «al-battah». Then he came to the Messenger of Allah (peace and blessings be upon him) and said: I have divorced my wife Suhaymah with «al-battah», and by Allah! I intended only one divorce. So the Messenger of Allah (peace and blessings be upon him) returned her to him. Then he gave her the second divorce in the time of Sayyiduna Umar and the third in the time of Sayyiduna Uthman.
With this narration the hadith is established as sahih, because Imam al-Shafi'i memorised it with great precision from the people of his own family and narrated it. Al-Sa'ib bin Abd Yazid (the father of Shafi' bin al-Sa'ib) was the brother of Rukanah, and Muhammad bin Ali bin Shafi', who was the paternal uncle of Imam al-Shafi'i, was an eminent elder of Quraysh in his time.