It is narrated from a man of Banu Thaqif that he heard Umar bin al-Khattab (may Allah be pleased with him) saying: If only I were able to make the waiting period of a slave woman one and a half menstrual cycles! That man said: Then make her waiting period a month and a half. Umar (may Allah be pleased with him) remained silent.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15453