How many find it of high morale value if you free a slave?

bukhari vol. 3 # 765 narrated kuraib; maimuna bint al-haret [one of mohammad's wives] told mohammad that she had manumitted [set free] her slave girl without taking permission of the prophet. on the day it was her turn to be with the prophet, she said,'' go you know, ''o'' allah's apostle, that i have manumitted my slave girl? he said have you really? she replied in the affirmative. he said, '' you would have gotten more reward if you had given her [the slave girl] to one of your maternal uncles...............so how many believe it was wrong of her to set the slave girl free instead of giving her to her uncle as instructed by the prophet of allah?