A man said to Sayyiduna Imran bin Husayn (may Allah be pleased with him): I divorced my wife openly and took her back secretly? Sayyiduna Imran (may Allah be pleased with him) said: "You divorced contrary to the waiting period (iddah), and took her back contrary to the Sunnah. Fear Allah and take witnesses."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15636