Ibrahim said that Sayyiduna Umar (may Allah be pleased with him) said: When a free woman is married to a slave and she has borne him a child, that child becomes free along with his mother's freedom, and his wala belongs to those who freed his mother. When the father is freed, the child's wala is then transferred to those who freed the father.
This is munqati' (its chain is broken), and it has been narrated from Umar (may Allah be pleased with him) with a connected chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الولاء / 21516