Emancipating a Slave who is jointly owned, buying a relative, and emancipating during an illness - Section 2 Mishkat al-Masabih 3400
Arabic hadith text
وَعَنْ أُمِّ سَلَمَةَ قَالَتْ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِذَا كَانَ عِنْدَ مكَاتب إحداكن وَفَاء فلنحتجب مِنْهُ» . رَوَاهُ التِّرْمِذِيُّ وَأَبُو دَاوُدَ وَابْنُ مَاجَهْ
Translation
Umm Salama reported God's Messenger as spying, “When a slave of one of you women has made an agreement to purchase his freedom and can pay the full price, she must veil herself from him.” Tirmidhi, Abu Dawud and Ibn Majah transmitted it.