TIRMIDHI 1261:
from Um Salamah —
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."
الترمذي ١٢٦١:
عن ام سلمه —
قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كَانَ عِنْدَ مُكَاتَبِ إِحْدَاكُنَّ مَا يُؤَدِّي فَلْتَحْتَجِبْ مِنْهُ