وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ إِذَا طَلَّقَ الْعَبْدُ امْرَأَتَهُ تَطْلِيقَتَيْنِ فَقَدْ حَرُمَتْ عَلَيْهِ حَتَّى تَنْكِحَ زَوْجًا غَيْرَهُ حُرَّةً كَانَتْ أَوْ أَمَةً وَعِدَّةُ الْحُرَّةِ ثَلاَثُ حِيَضٍ وَعِدَّةُ الأَمَةِ حَيْضَتَانِ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umarsaid, "When the slave divorces his wife twice, she is haram for himuntil she has married another husband, whether she is free or a slave.The idda of a free woman is three menstrual periods, and the idda of aslave-girl is two periods. Translation Not Available

Book Ref: Muwatta Imam Malik Book 29 Hadith 1210
Web Ref:  Muwatta Imam Malik Book 29 Hadith 50