Ibn Ishaq says: A man would divorce his wife and then take her back before the iddah ended; there was no limit to divorce. Then a man from the Ansar divorced his wife, as their life together was not good. He said: I will leave you neither unmarried nor with a husband. He would divorce her, and when the end of her iddah drew near, he would take her back. So Allah revealed this verse. Hisham bin Urwah narrates from his father that Sayyidah Aishah (may Allah be pleased with her) said: "Divorce is twice; then (either) retaining in a good manner or releasing with kindness" [Surah al-Baqarah: 229]. So three divorces were fixed for them: after one or two there is taking back, and after the third, taking back is not valid. Allah's saying: "When you divorce women, divorce them for their iddah, and count the iddah, and fear Allah" up to His saying "a clear immorality" [Surah al-Talaq: 1]. And the hadith of Rukanah about taking back has already passed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرجعة / 15151