Rashi on Leviticus 5:12/רש"י על ויקרא ה׳:י״ב

1חטאת הוא IT IS A SIN-OFFERING — Here, too, the apparently redundant words intimate: if the קמץ has been taken from it and has been burnt for the purpose of (i.e. having in mind that it is) a sin-offering it is valid; if, however, this was done not for its purpose (i. e. the priest had another offering in mind when officiating) it is invalid (Sifra, Vayikra Dibbura d'Chovah, Chapter 19 9).