Which Mizbe'ach is "ha'Mizbe'ach" referring to.
Oznayim la'Torah: It is referring to the Mizbe'ach that the Torah mentioned immediately after the Aseres ha'Dibros - at the end of Parshas Yisro.
What was the height of the Mizbe'ach?
Rashi #1 (citing R. Yehudah, Zevachim 60a): It was three Amos tall, as the Torah records.
Rashi #2 (citing R. Yossi, Zevachim 60a.): It was ten Amos tall (twice its length). 1
Based on a Gezeirah-Shavah "Ravu'a" "Ravu'a" from the Mizbe'ach ha'Ketores. And the Torah gives the height as three Amos, because that was the height of the Mizbe'ach (excluding the K'ranos) above the Sovev - a walkway for Kohanim around the Mizbe'ach (Rashi). Refer also to Bamidbar, 3:27:1:1.
Having given the measurements as five Amos by five Amos, why does the Torah add the word "Ravu'a"?
Refer to 27:1:1:2*.
Oznayim la'Torah: Square is not dependent only on the four sides being equal, but also on the four corners, which must all be at an angle of ninety degrees.
What if the Mizbe'ach was not exactly square?
Zevachim, 62a: Wherever the Torah inserts the word "ha'Mizbe'ach", it is crucial to the Mitzvah, 1 and without it, the Mizbe'ach is Pasul. 2
Though the measurements are not, which explains why, in the second Beis-Hamikdash, the Mizbe'ach measured thirty-two by thirty-two Amos.
The same D'rashah pertains in Tetzaveh, 29:13 to the K'ranos and to the Y'sod there in Pasuk 12, and in Tzav, Vayikra 6:7, to the Kevesh. See Torah Temimah, note 5.
QUESTIONS ON RASHI
Rashi writes that one opinion holds that the Mizbe'ach was ten Amos tall. How could the Kohanim place blood on the corners, and wood, limbs and Cheilev on the fire on top?
