Pesachim 63A

לימא קסברי אחרים אינה לשחיטה אלא בסוף, וכדרבא. דאמר רבא: עדיין היא מחלוקת.

The Talmud asks: Let us say that Aḥerim hold that slaughter is not legally significant until the end, meaning that the slaughter is considered to take place only at the end of the rite and not during the time it takes to perform the act of slaughter, in accordance with the opinion of Rava in a different context. As Rava said: It is still a dispute, meaning that the disagreement whether one is held accountable only for his first expression or also for the conclusion of his statement applies even when it is one’s clear intention that the status he wishes to confer should apply only at a particular time, e.g., if one says that an animal should be consecrated as a burnt-offering until midday and from then on as a peace-offering (Rabbeinu Ḥananel). The opinion of R' Meir, referred to here as Aḥerim, is that one is held accountable only for his first expression.

הילכך: הקדים מולין לערלים ⁠— מולין חיילי, ערלים לא חיילי. הקדים ערלים למולין ⁠— ערלים חיילי, מולין לא חיילי.

Therefore, based on these two assumptions, if one put the circumcised people before the uncircumcised people, his statement with regard to circumcised people applies but his statement with regard to uncircumcised people does not apply. If the slaughter is legally considered to take effect in a single instant, and if one said that his intention is for circumcised people at that moment, his statement takes effect. In the reverse case, if one put the uncircumcised people before the circumcised people, his statement with regard to uncircumcised people applies, but his statement with regard to circumcised people does not apply.