How many believe that slavery is wrong?

bukhari vol. 3 book 47 # 765 al-harith, one of mohammad's wives, told mohammad she had manumitted her slave girl without taking the permission of the prophet, on the day it was her turn to be with the prophet. she said, '' do you know, ''o'' allah's apostle, that i have manumitted [freed] my slave girl? he said ''have you really''? she replied in the affirmative. he said, ''you would have got more reward if you had given her to one of your maternal uncles.................. so how many agree that al-harith was wrong for freeing her slave girl instead of giving her to one of her maternal uncles, like the prophet of allah suggested?