Why didn't the Prophet (PBUH) emancipate the slave who pledged allegiance to him for emigration, after his master came to claim him, and instead bought him for two black slaves?

It is not authentically reported that the Prophet, peace and blessings be upon him, traded in slaves. Rather, the aforementioned hadith clarifies that a slave came and pledged allegiance to the Prophet, peace and blessings be upon him, for migration, and the Prophet did not know that he was a slave. When his master came to claim him, the Prophet, peace and blessings be upon him, bought him for two slaves. This was due to his noble character, his desire to attain the reward of freeing a slave, and his dislike for a migrant to return disappointed. Thus, the slave became free. This was an act of generosity on his part, not a trade, for the fundamental state of people is freedom.