וְאִם־לֹ֨א תִמְצָ֣א יָדָהּ֮ דֵּ֣י שֶׂה֒ וְלָקְחָ֣ה שְׁתֵּֽי־תֹרִ֗ים א֤וֹ שְׁנֵי֙ בְּנֵ֣י יוֹנָ֔ה אֶחָ֥ד לְעֹלָ֖ה וְאֶחָ֣ד לְחַטָּ֑את וְכִפֶּ֥ר עָלֶ֛יהָ הַכֹּהֵ֖ן וְטָהֵֽרָה׃ (פ)
그 여인의 힘이 어린 양에 미치지 못하거든 산비둘기 둘이나 집비둘기 새끼 둘을 가져다가 하나는 번제물로, 하나는 속죄제물로 삼을 것이요 제사장은 그를 위하여 속할지니 그가 정결하리라
Rashi
אחד לעלה ואחד לחטאת THE ONE FOR A BURNT-OFFERING AND THE OTHER FOR A SIN-OFFERING — Scripture puts it (the עולה) first only by way of mention, but so far as offering it is concerned the sin-offering precedes the burnt-offering; thus do we learn in the Treatise Zevachim 90a, in the chapter commencing כל התדיר .
Kli Yakar
And the priest shall make atonement for her, and she shall be clean. This atonement is for the primordial sin of Eve that caused her the pain of childbirth, and in her pain perhaps she spoke harshly toward Heaven saying, “’If so, why am I’ pregnant with toil and suffering?” And proof of this is from what is written, and she shall be clean from the source of her blood — from that source that was opened for sin and impurity, for it [the sin] caused her all this, namely the sin of Eve as mentioned. Also, the language of damehah [her blood] includes the sin, from the expression their blood is upon them (Leviticus 20:27).
Sforno
וכפר עליה, for during all the days that she had been excreting blood her thoughts had been preoccupied with the phenomenon of semen, etc, and she had therefore not been in a fit state of mind to enter the precincts of the Temple and offer sacred matters.