The Sunnah way of divorce is that he divorces her while she is in a state of purity and without having had intercourse with her.
أخبرنا عمرو بن علي قال حدثنا يحيى عن سفيان عن أبي إسحق عن أبي الأحوص
طلاق السنة أن يطلقها طاهرا في غير جماع
[Hasan] see the previous hadith. It is in Kubra, no. 5588, and Ibn Majah, no. 2020, narrated it from the hadith of Yahya Qattan and others.