Rashi on Exodus
ויזרק means sprinkling — he sprinkled it on the people (not he threw it against the people, as this word might imply; cf. e. g., Exodus 9:8: וזרקו משה השמימה). The Targum, however, renders it by: and he poured it (the blood) upon the altar as atonement for (על) the people, adding the words “upon the altar”, and taking על העם to denote “on behalf of the people”, i. e. he poured it out to atone for the people.
Tur HaArokh
ויזרוק על העם, “he sprinkled on the people.” Some commentators understand the word על here to mean בעד, “on behalf of.” We have a parallel to this in Numbers 17,12 ויכפר על העם “Aaron atoned on behalf of the people.”