Gittin 41 - When Beit Hillel was convinced
One who is half-slave and half-free man (one of the two owners emancipated his share) works one day for his master and one day for himself - says Hillel school.
Shammai school says: You have solved his master's dilemma, but you have not solved his own. For it is impossible for him to marry a slavewoman, because half of him is already a free man. And it is impossible for him to marry a free woman, because half of him is still a slave. And Hillel school reversed itself to rule in accordance with the words of Shammai school.
Art: The Jewish Wedding by Moritz Oppenheim