Al-’Asqalani, explanation of Al-Bukhari’s Hadith collection
Now al-Bukhari’s statement “if one interpreter is admissible” indicates the disagreement on this point […] Accepting one interpreter as sufficient in the opinion of the Hanafi school of fiqh […] According to Al-Shafi’i (and reflecting the prevalent opinion among the Hanbali school), if the judge does not know the language of a litigant, then only two competent interpreters are acceptable. For the interpreter would convey to the judge what is not accessible to him concerning governance, a case that requires all the conditions of competency, as in giving testimony.4 The interpreter would also inform the judge of something that he does not know, as in communicating to him a statement from outside his court.
Then al-Bukhari excerpted part of the narrative of Abu Sufian with Heraclius […] the purpose of which lies in the part “Heraclius said to his interpreter: ‘Tell him’,” etc.
Ibn Battal said: “Al-Bukhari did not include the Heraclius narrative as evidence that a non-Muslim interpreter is admissible (as Heraclius’ interpreter was an adherent of the faith of his people [i.e., a Christian]), but to show that interpreters in other nations were treated as informers, not as witnesses.
In his al-Ahkam (Legal Judgments), al-Muhib al-Tabari mentioned using one interpreter as sufficient, referencing the hadith of Zaid Ibn Thabit and the reports about ’Umar and Ibn ’Abbas. He said: “Those who opined for one interpreter used the overt meaning of these narratives as evidence” […]
As for the narrative of ’Umar with the woman, it seems from the context that it concerned legal judgment, for ’Umar absolved the woman from the legal punishment for adultery, owing to her ignorance that this practice was forbidden, after he had formally charged her and had been about to implement the punishment to her. In this, he relied on the information provided by one person who translated from her language.
The narratives of Abu Jamra with Ibn ’Abbas, and that of Heraclius (where interpreting was purely informative), may have been cited by way of support and confirmation […]
What we can glean from al-Bukhari is that a single interpreter is admissible in cases that do not require a judge. However, this is not the point of dispute, but rather what happens in cases brought before a judge, most of which can be seen as legal judgment. This is especially the case for those who say that the conduct of a judge by itself is judgment.
Ibn al-Munthir said:
To this, it can be replied that the Prophet (BPUH) cannot be compared with other rulers, for, unlike them, he could have knowledge through divine revelation of what was not readily available to him. Therefore, we can conclude that what is delivered as information can be conveyed by one interpreter, whereas what is delivered as testimony requires the minimum number [of two].
Al-Karabisi reported that the Rashidun Caliphs,6 as well as the kings that came after them, had only one interpreter each.
Ibn al-Tin reported of ‘Abd al-Hakam: “No one can interpret save a free and competent man. When the interpreter delivers a statement, then it would be best for two witnesses to hear it and submit it to the adjudicator.”