Is paying the bond to free a convict equivalent to freeing a slave?
2-4-2013 | IslamWeb
Question:
Is paying the bond to free someone from jail included in the meaning of freeing a slave?
Answer:
All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Paying the bond to free a jailed person is not included in the meaning of freeing a slave that is stated in the Sharee‘ah texts.
However, if a person is a Muslim who is imprisoned by the disbelievers, Muslim jurists hold that the Zakah channel allocated to freeing slaves can be applied in the case of freeing him according to the opinion of the Hanbali school of Fiqh.
Al-Buhooti, a Hanbali scholar 
said: "It is permissible to ransom by it (i.e. Zakah) a Muslim prisoner who is in the hands of the disbelievers. He (i.e. the author) explicitly stated this since it is like freeing a slave."