The gemara says that according to beis hillel, all korbanos including chatas only require a minimum of one matana which is me'akev, but ideally require 3 matanos. This is learned from the fact that there are 4 pesukim that reference the keren of the mizbei'ach. The gemara asks that perhaps all 4 pesukim teach the lichatchila, and there is nothing at all that is me'akev. The gemara answers - כפרה בכדי לא אשכחן, without doing any matanos it is impossible to achieve atonement. Therefore, one of the pesukim would have to be li'ikuva.
The Cheshek Shlomo raises an interesting question based on Shmuel 26b who darshens from the pasuk that as far as the owner receiving a kappara the blood can be put anywhere on the miz'beiach. Shmuel darshens from the pasuk of ואני נתתיו לכם על המזבח לכפר that as soon as the blood reaches the mizbei'ach the owner achieves atonement, even if it didn't hit the right part of the mizbei'ach. The cheshek shlomo understands that according to Shmuel it shouldn't matter if the blood hits the korner or hits the yesod, so long as it hits the mizbei'ach the owner is forgiven. Based on this, our gemara that says we require a minimum of placing the blood on one corner to achieve atonement because kappara can't come for nothing. But how does the gemara know this, perhaps all 4 pesukim require lichatchila the blood to be placed on all 4 corners, but bidieved even if it isn't put on any corners just on the yesod, it would give kappara? Why does the gemara consider the blood being poured on the yesod and not on the corner to be כפרה בכדי - atonement for nothing?