What were the "Techashim"?
Rashi: They was a kind of multicolored Chayah that existed only at that time. 1
Shabbos, 28b: The Tachash was a unique creature that existed in the time of Moshe. The Chachamim could not decide whether it was a Chayah or a Beheimah. It appeared to Moshe for that time only 2 - he used in to make the Mishkan and it disappeared.
From where did they obtain Atzei Shitim (acacia wood) in the desert?
Rashi: Ya'akov Avinu, knowing via Ru'ach ha'Kodesh that his children were destined to build a Mishkan in the desert, brought acacia 1 trees 2 with him to Egypt and planted them, and instructed his children that, when they left Egypt, they should cut them down and take them with them.
Hadar Zekenim (in Pasuk 3): It grew in large forests in the desert. 3
Midrash Tanchuma: Refer to 25:5:3:2. Ya'akov obtained the wood from the Eishel (orchard) that Avraham Avinu planted in Be'er-Sheva, 4 which he cut down and transplanted.
Da'as Zekenim, Hadar Zekenim (on Pasuk 3): It must be an extremely light wood, since eight oxen (of the B'nei Merari) were able to pull the wagons holding forty-eight Kerashim (each measuring ten by one and a half by one Amah), ninety-eight Adanim, and over fifty Amudim (staves to hold the curtains of the Chatzer and Paroches...)
Da'as Zekenim: The Beri'ach ha'Tichon (the middle bolt) was from Ya'akov's staff. Refer also to 26:28:1:2.
Hadar Zekenim : As the Torah writes in Balak Bamidbar 25:1 "Va'yeishev Yisrael ba'Shitim", and in Yehoshua 2:1 "va'Yishlach Yehoshua... min ha'Shitim" - so-called after the forest of acacia-trees. Se also Yeshayah, 41:19.
Oznayim la'Torah: In order to perform Chesed with whoever passed by. See Vayeira, Bereishis, 21:33 It transpires that the Mishkan was built on the three pillars on which the world stands: On Torah (the Aron); On Avodah (the Mizbe'ach) and on Gemilus Chasadim (the boards that comprised the Mishkan).
