Mishnayos Kerisos Perek 6 Mishnah 7

In the case of one who designates a sin offering for his performance of an unwitting sin and dies, his son shall not bring it in his stead, neither on behalf of his father nor for his own unwitting sin, even if it was the same transgression. Likewise, one may not bring a sin offering by reassigning it from the sin for which it is designated to atone and sacrificing it for atonement of another sin. Even if he designated a sin offering as atonement for forbidden fat that he unwittingly ate yesterday, he may not bring it as atonement for forbidden fat that he unwittingly ate today, as it is stated: “And he shall bring his sin offering, an unblemished female goat, for his sin that he has sinned” (Leviticus 4:28), indicating that he does not satisfy his obligation until his offering is brought for the sake of the sin for which he designated it.

הַמַּפְרִישׁ חַטָּאתוֹ, וּמֵת, לֹא יְבִיאֶנָּה בְנוֹ אַחֲרָיו. וְלֹא יְבִיאֶנָּה מֵחֵטְא עַל חֵטְא, אֲפִלּוּ עַל חֵלֶב שֶׁאָכַל אֶמֶשׁ לֹא יְבִיאֶנָּה עַל חֵלֶב שֶׁאָכַל הַיּוֹם, שֶׁנֶּאֱמַר (ויקרא ד), קָרְבָּנוֹ עַל חַטָּאתוֹ, שֶׁיְּהֵא קָרְבָּנוֹ לְשֵׁם חֶטְאוֹ: