It was
narrated that Jabir said:
“A slave came and gave his pledge to
the
Prophet (ﷺ), pledging to emigrate, and the Prophet (ﷺ) did not
realize that he was a slave. Then his master came looking for him,
and
the Prophet (ﷺ) said: ‘Sell him to me,’ and he brought him
in
exchange for two black slaves. Then after that he did not accept
the
pledge from anyone until he had asked whether he was a slave.”