That the Messenger of Allah ﷺ said: "When one of you (women) has a Mukatab ho has with him what will fulfill (the Kitabah) then observe Hijab from him."

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كَانَ عِنْدَ مُكَاتَبِ إِحْدَاكُنَّ مَا يُؤَدِّي فَلْتَحْتَجِبْ مِنْهُ