Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: Whoever intends a divorce according to the Sunnah should adopt the method that Allah, the Lord of Might, has commanded: he should wait for purity after menstruation, then divorce her in that purity without intercourse and make two men witnesses; then he should wait for purity after (another) menstruation, and if he wishes he may take her back, and if he wishes he may divorce.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14946