Midrasch zu Schemot 29:38

2) R. Yossi Haglili says: From (Shemoth 29:37): "All that touches the altar shall become consecrated," I would think that both things fit for the altar and things unfit for the altar are herein subsumed; it is, therefore, written (Shemoth 29:38): "And this is what you shall offer upon the altar: lambs, etc.": Just as lambs are fit for the altar, (so all thus fit are included) — to exclude that which is not fit.

We are taught that R. Jose b. R. Juda says: "A fire in the shape of an ark, in the shape of a table and in the shape of a candle-stick, came down from heaven, which Moses saw and make like those shapes, for the passage says (Ex. 25, 40) And see that thou make them after their pattern, which is being shown thee in the mount." According to this then the verse (Ib. 26, 30) And thou shalt rear up the Tabernacle according to its rules thereof which hath been shown thee in the mount, does it also mean [that a fire in the shape of the Tabernacle was shown to Moses]? Here the passage says, according to its rules, but there [concerning the ark, the table, and the candle-stick] it is written according to their pattern. R. Chiya b. Abba said in the name of R. Jochanan that Gabriel attired himself with an apron and showed Moses how to make the candle-stick, as it is written (Num. 8, 4) And this was the work of the candle-stick. In the academy of R. Ishmael it was taught that three things were difficult for Moses to comprehend, until the Holy One, praised be He! showed them to him. The three things are: The candle-stick, the new moon and the [distinction between the clean and unclean] reptiles. Concerning the candle-stick we infer from the above-mentioned passage, And this was the work of the candle-stick; the new moon, as it is written (Ex. 12, 2) This month shall be unto you the beginning of months; reptiles, as it is written (Lev. 11, 29) And these shall be unclean unto you. According to some authorities also the laws concerning slaughtering were difficult for Moses to understand, as it is written (Ex. 29, 38) And this is what thou shall offer upon the altar.

"the one lamb, etc." Why is this written? (It seems superfluous.) Because it is written (3) "And you shall say to them: This is the fire-offering, etc." and (Shemot 29:38) "And this is what you shall offer upon the altar," I might think that he should sacrifice four. It is, therefore, written "the one lamb" — not more than one.