Zevachim 52 - The Base of the Altar
The base of the Altar was a protrusion at its bottom, a step, one ell (about 2 feet) high and one ell wide. It ran around the Altar, except its eastern side . The blood of burnt offerings was thrown on this base, that is, on its top flat part, or above it, on the Altar's wall. How do we know this?
The Torah writes, "onto the base of the burnt-sacrifice Altar." From the extra word "Altar" we understand that the blood is to be thrown on the top of the base, which is similar to the roof (top) of the Altar.
Rabbi Ishmael says that the verse is not needed for this, and that it can be derived by logic: if the remnant of the blood of the sin offering, which, being the remnant, does not atone for anything, is poured on the base, then certainly the first application of the blood of the burnt offering, which does atone, definitely needs the base.
Then what does rabbi Ishmael do with the verse, since he derives his law without it? He uses it to expand the law about the base to all other types of sacrifices.
Art: Orazio Riminaldi - Sacrifice Of Isaac C. 1625