Which verse encourages the emancipation of slaves: (..........then the freeing of a slave)?

The Qur'an encourages the manumission of slaves in several verses, among them the words of Allah Almighty in Surat Al-Balad: "But he has not attempted the arduous ascent. And what can make you know what is the arduous ascent? It is the freeing of a slave," which indicates that freeing a slave is among the reasons for overcoming difficulties in the Hereafter. Also, Allah Almighty said: "So write [a contract] with them if you recognize goodness in them and give them from the wealth of Allah which He has given you." Allah has also made the freeing of a slave an expiation for some sins, such as killing and Zihar (a form of divorce), which confirms Allah Almighty's love for the manumission of believing slaves.