Narrated 'Abdullah bin 'Umar:
Allah's Apostle said, "Whoever frees his share of a common slave and he has sufficient money to free him completely, should let its price be estimated by a just man and give his partners...
O Allah, I ask You by Your mercy, which encompasses all things, that You forgive me.
Info: Ibn Majah 1/557 from a supplication of Abdullah bin 'Amr. Al-Hafidh graded it as good in his checking of An-Nawawi's Kitabul-'Athkdr. See Sharhul- Athkar 4/342.