פירוש על בבא מציעא 237:5

Before King Shapur -- It appears to me that this is the actual King Shapur who was King of Persia and was a legal expert. They said the teaching of Rabbi Shimon in the mishnah before him and he praised it, saying, 'אפריון נמטייה לר״ש' -- 'May [Rabbi Shimon] receive grace from us for this matter!' However, some say King Shapur here is [the sage] Shemuel, for in several places he is called this. However, this does not fit, for then what does it mean that 'they said [this teaching]'? If this refers to the teaching of Rabbi Shimon in the mishnah, did Shemuel not know the mishnah? And if this refers to the teaching of Ephrayim the Scribe, if Resh Lakish had not said that the law accord with Rabbi Shimon, did Shemuel not know the law well enough to praise Rabbi Shimon before hearing in the name of Resh Lakish that the law accords with him?

King Shapur -- The correct explanation appears to accord with Rashi (that King Shapur here refers to the actual King Shapur, not the sage Shemuel who is sometimes called King Shapur), for King Shapur was an expert in Jewish law, as it says at the end of Tractate Avodah Zarah (76b), that he stabbed the knife ten times into hard earth when he cut the citron with a knife for Rav Yehudah.

'Apiryon' (אפריון) -- 'our grace.'