Zevachim 11B

אמר לו רבי יהושע: מצינו מותר חטאת בא עולה, ואין מותר עולה בא חטאת;

R' Yehoshua said to him: This inference is not valid, as we find that a leftover sin offering, e.g., one bought with money left over from funds dedicated to the acquisition of a sin offering, is brought as a burnt offering, whereas a leftover burnt offering is not brought as a sin offering.

ומה חטאת, שמותרה בא עולה ⁠– שחטה לשם עולה, פסולה; עולה, שאין מותרה בא חטאת ⁠– שחטה לשם חטאת, אינו דין שתהא פסולה?!

And according to R' Eliezer’s logic, one should derive a fortiori: Just as with regard to a sin offering, whose leftover is brought as a burnt offering, nevertheless, if one slaughtered it for the sake of a burnt offering it is unfit, so too, with regard to a burnt offering, whose leftover is not brought as a sin offering, if one slaughtered it for the sake of a sin offering, isn’t it logical that it should be unfit? Yet, the halakha is that a burnt offering slaughtered for the sake of a sin offering is fit.

אמר לו רבי אליעזר: לא; אם אמרת בחטאת ⁠– שכן כשרה לשמה כל השנה כולה, תאמר בפסח ⁠– שאינו כשר לשמו אלא בזמנו?! הואיל והוא פסול לשמו, דין הוא שיפסלו אחרים לשמו.

R' Eliezer said to him: No, if you said that this is the halakha with regard to a sin offering, that another offering sacrificed for its sake is fit, this is only because a sin offering is fit when sacrificed for its sake all year long. should you also say that this is the halakha with regard to a Paschal offering, which is fit when sacrificed for its sake only at its designated time? Since a Paschal offering is unfit when sacrificed for its sake during the rest of the year, it is logical that other offerings should be disqualified when sacrificed for its sake at its designated time.