Muwatta Malik · Hadith 1489

حَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ الْمُكَاتَبُ عَبْدٌ مَا بَقِيَ عَلَيْهِ مِنْ كِتَابَتِهِ شَىْءٌ ‏.‏

Malik related to me from Nafi that Abdullah ibn Umar said, "A mukatab is a slave as long as any of his kitaba remains to be paid

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).