Is the testimony of a single Muslim confirming he granted Aman to a captive accepted?

Primary text

There are differing views. According to the strict view of Ahmad, it should be accepted, similar to a judge stating after his removal that he had ruled in favor of someone. According to Abu Al-Khattab, the Aman itself is valid, so his report of it is accepted, like a judge during his tenure. The probable opinion is that it is not accepted because he does not have the authority to grant Aman in that situation, so his admission of it is not accepted, akin to admitting a debt owed by another person. This latter view is held by Al-Shafi'i and Abu Ubaidah.