On the BBC Slavery in Islam page
the Prophet... stated that freeing slaves was the act that God found most acceptable
I'm trying to pinpoint the hadith they're referring to.
Question: Is there a hadith to the effect of "freeing slaves was the act that God found most acceptable"?
(And if there is, what is its level of authenticity?)
It seems likely that the BBC were paraphrasing, so I'm not expecting to find a word-for-word exact match.
site:sunnah.com freeing slaves and
site:sunnah.com freeing slaves was the act that God found most acceptable comes up with some related ahadith, e.g.:
"...any Muslim man who frees a Muslim man, then it is his salvation from the Fire..." Jami' at-Tirmidhi 1547
"We were ordered to free slaves at the time of lunar eclipses." Sahih al-Bukhari 2520
"Abu Huraira said (to the Prophet), 'I make you witness that the slave is free for Allah's Cause.'" (Sahih al-Bukhari 2532)
But these are not good fits to the BBC's hadith.
There's mention of freeing slaves in the Qur'an (e.g. 9:60), but I don't think these are what the BBC is referring to.