According to the Mishna (2a), if a sacrifice was brought with the wrong intention – e.g. where, at the time of slaughter, the owner thought that this animal was to serve as a different sacrifice – it remains a valid sacrifice, although it does not count for its original purpose and, if he was obligated to bring a korban, the owner will have to bring another sacrifice. The only exceptions are the Passover sacrifice (korban Pesaḥ) and a sin-offering (korban ḥattat), which must be brought with the proper intent. Rabbi Eliezer argues that a korban asham – a guilt-offering – also must be brought with the proper intent. His reasoning, as it appears in the Mishna, is that the asham is similar to the ḥattat in that they both come to atone for sin. Therefore, if the ḥattat must be brought with the proper intent, the asham must be brought with the proper intent, as well.
On today’s daf, a baraita is brought where we find an expanded version of this argument. Rabbi Yehoshua responds to Rabbi Eliezer that a korban ḥattat and a korban asham are not similar and cannot be compared, since the blood from the sin-offering is sprinkled on the upper part of the altar.
The altar was divided into two – an upper half and a lower half. As Rashi explains, in the mishkan the altar had a ledge halfway up (see 27:5) while in the Temple the altar was divided by ḥut ha-sikra – a red line that was drawn in order to divide the top half of the altar from the bottom half in order to show where the blood of the different sacrifices had to be sprinkled. Of all the sacrifices, only a sin-offering brought from an animal and a burnt-offering brought from fowl had their blood sprinkled on the upper part of the altar; blood from all other sacrifices was sprinkled on the lower part of the altar.
Ultimately, Rabbi Eliezer explains that his ruling stems from the passage in Sefer Vayikra (7:7) that juxtaposes the sacrifices of the ḥattat and the asham, indicating that their laws parallel one another. This juxtaposition, referred to as a hekesh, is accepted by all. Those who disagree with Rabbi Eliezer argue that it comes to teach us a different law that is shared by these two sacrifices – that each of them needs semikha, i.e. that the owner must place his hand and lean on the sacrifice as it is being brought.