The book of Vayikra begins its discussion of sacrifices with the olah (elevation-offering), the wholly burnt offering (Vayikra 1:2-13). After the animal is slaughtered and a portion of its blood is dashed on the sides of the Altar, it is prepared to be burned on the Altar. While it is flayed, part of the animal is washed by the Kohen:
And its inner organs and legs shall he wash with the water (YIRCHATZ BA’MAYIM) (verse 9; cf. verse 13 here).
Similar descriptions are found in Vayikra 8:21 and 9:14, and in Shemot 29:17.

What is the purpose of this washing? Is it for purification, or simply cleansing?

The Midrash (Torat Kohanim, Nedava 6:7) decides that this is not purification in a mikveh:
“You might have said that, just as elsewhere, the washing spoken of is [immersion] in forty seahs of water, so too here the washing spoken of should require [immersion in] forty seahs. Therefore the text says with water (BA’MAYIM), meaning of any kind.”

Chizkuni (R. Chizkiya ben Manoach, mid-13th Century) further notes that when the Torah uses the verb R-CH-TZ to mean a person immersing in water, Onkelos usually translates it using the Aramaic word that means “to immerse” (S-CH-Y, similar to the Hebrew root S-CH-H, which means “to bathe”). However, whenever the Torah speaks of washing a sacrifice, Onkelos translates R-CH-TZ using the Aramaic root CH-L-L, which means “to empty out.”

This washing therefore is functional, removing any semi-digested food. The dirty inner parts of the animal are scrubbed to make the offering suitable for Hashem’s Altar. In the Temple, the rumen was washed in a washing chamber located on the south wall of the Azara, east of the Water Gate, and the intestines, which require at least three washings, were cleaned out on marble tables between the columns in the slaughtering area (Tamid 4:2; Rambam, “Laws of Offering the Sacrifices” 6:6).

This requirement of washing is found only with reference to the olah, and not with any other sacrifice. Bechor Shor (R. Yosef Bechor Shor, born c. 1140) explains why:
“When it comes to the sin-offering and the guilt-offering which are eaten by the Kohanim, as well as the peace-offering which is eaten by the owners, whoever eats of them will wash them if he so desires. The [olah], however, is served at the table of the King, and must be prepared with honor.”
When a person eats, he will prepare his food as he sees fit; but the olah is not eaten by man, but rather offered in its entirety to Hashem, so it must be cleansed of any unseemly parts.

Even though the washing of the olah is not for purification, but cleansing, the Torah still requires water (BA’MAYIM), and not any other liquid:
“BA’MAYIM – with water, and not with wine; with water, and not with a mixture of wine and water (Torat Kohanim, loc. cit.; Zevachim 22a).”

What is the source of this water? The Talmud (Zevachim, loc. cit.) offers two different views with reference to using the water from the Kiyor― the Laver built for the Kohanim to wash their hands and feet― for washing out the inner parts of the olah. One source says that while the word BA’MAYIM requires water, and no other liquids, it comprises all water, including – perhaps, especially – the water of the Kiyor. Another source says that BA’MAYIM means unspecified water, and not water that has acquired “an accompanying name,” whereas the water taken from the Kiyor is not known simply as “water,” but “Kiyor-water,” and is thus unsuitable for this purpose. Rambam (ibid.) says that
“all water is fit”
for cleaning out the olah, which means only that the water need not come from a special source, like a flowing stream or rain water; it can come from any source. He side-steps the issue of whether water that has acquired “an accompanying name” – such as Kiyor-water – is valid or invalid. The commentary on Rambam, Mishneh LaMelech (R. Yehudah Rosannes, 1657-1727) admits that he does not know why Rambam has omitted this issue.

It is surprising, however, that the Temple of Shlomo is not cited as a source. Because, in the description of the Temple, we read:
And he made ten lavers, and put five on the right and five on the left, to wash in them, parts of the offering of the olah they would wash in them; but the basin (Yam, sea) was for the Kohanim to wash in (Divrei HaYamim II 4:6).
This seems to state that Kiyor-water is valid for cleaning out the ‘olah. And yet, the Talmud never introduces this source as a proof!

Rashi, however, in his commentary on Divrei HaYimim and on the parallel verse in Melachim I (7:38), anticipates our question. He says that Shlomo’s ten lavers, five placed on each side of Moshe’s original Kiyor, were those used for cleansing the parts of the olah. They were merely receptacles for holding the water needed to wash the olah, and the water in them never acquired the “accompanying name” of “Kiyor-water”; only the water in Moshe’s original Kiyor, used by the Kohanim to wash their hands and feet, has an “accompanying name.” We still do not know whether Kiyor-water can be used to cleanse the olah, because the verses in Divrei HaYamim and Melachim do not discuss such water one way or the other. The amazing thing is that Rashi apparently has no source for this reading. But it is Rashi’s vast knowledge of the teachings of our Sages that suggests it to him.

The olah is the offering of utter devotion to Hashem, born of the yearning to come as close as possible to the Creator. Nevertheless, lest we think that this aspiring should suffice, that Hashem would somehow “overlook” our ignoring of propriety, the laws of washing the olah tell us: first be sure you are cleansed from within of even the most common stain – and do so using Hashem’s first, simplest creation, water – before ascending towards Him.