Muwatta Malik, hadith 1220

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ رَجُلٍ، مِنَ الأَنْصَارِ أَنَّ امْرَأَتَهُ، سَأَلَتْهُ الطَّلاَقَ فَقَالَ لَهَا إِذَا حِضْتِ فَآذِنِينِي ‏.‏ فَلَمَّا حَاضَتْ آذَنَتْهُ فَقَالَ إِذَا طَهُرْتِ فَآذِنِينِي فَلَمَّا

Yahya related to me from Malik from Yahya ibn Said from a man of the Ansar that his wife asked him for a divorce, and he said to her, "When you have had your period, then tell me." When she had her period, she told him. He said, "When you are purified then tell me." When she was purified, she told him and he divorced her. Malik said, "This is the best of what I have heard about it