ועצי שטים, “and (boards of) acacia trees.” There were forests in the desert in which these trees grew. This is why the Israelites were described as dwelling at Shittim, (Numbers 25,1) The wood of these trees is light in weight and pleasant to look at. The 48 boards of the Tabernacle, as well as the pillars at the entrance and between the Sanctuary and the Holy of Holies were constructed of that wood and transported on the wagons donated by the princes as per Numbers 3,3634 and 4,3132. So were the bolts that were attached to link the boards to one another. They were all transported on these four wagons which were pulled by eight oxen under the supervision of the Levites from the family of Merari. (Numbers 7,8) Seeing that the boards were ten cubits (six meters) long each and one and a half cubits thick, it is extremely likely that the wood from which they were cut was light in weight.
From Wikipedia:
Faidherbia is a genus of leguminous plants containing one species, Faidherbia albida, which was formerly widely included in the genus Acacia as Acacia albida. The species is native to Africa and the Middle East and has also been introduced to Pakistan and India.[3] Common names include apple-ring acacia[4] (their circular, indehiscent seed pods resemble apple rings),[5] and winter thorn.[3] The South African name is ana tree.[3][6]
It is a thorny tree growing up 6–30 m (20–98 ft) tall and 2 m (6.6 ft) in trunk diameter. Its deep-penetrating tap root makes it highly resistant to drought. The bark is grey, and fissured when old. There are 11,000 seeds/kg.[citation needed]
A population is found in relict groves in Israel (in the Shimron nature reserve, near the community settlement of Timrat). All of the trees in a given grove are genetically identical and seem to have multiplied by vegetative reproduction only, for thousands of years
(ד) וַיִּסַּע יִשְׂרָאֵל וְכָל אֲשֶׁר לוֹ וַיָּבֹא בְּאֵרָה שָׁבַע (בראשית מו, א), לְהֵיכָן הָלַךְ, אָמַר רַב נַחְמָן שֶׁהָלַךְ לָקֹץ אֲרָזִים שֶׁנָּטַע אַבְרָהָם זְקֵנוֹ בִּבְאֵר שָׁבַע, הֵיךְ מָה דְאַתְּ אָמַר (בראשית כא, לג): וַיִּטַּע וגו'. כְּתִיב (שמות כו, כח): וְהַבְּרִיחַ הַתִּיכֹן בְּתוֹךְ הַקְּרָשִׁים, אָמַר רַבִּי לֵוִי וְהַבְּרִיחַ הַתִּיכֹן שְׁנַיִם וּשְׁלשִׁים אַמָּה הָיוּ בוֹ, מֵהֵיכָן מָצְאוּ אוֹתוֹ לַשָּׁעָה, אֶלָּא מְלַמֵּד שֶׁהָיוּ מֻצְנָעִין עִמָּהֶם מִימוֹת יַעֲקֹב אָבִינוּ, הֲדָא הוּא דִכְתִיב (שמות לה, כד): וְכֹל אֲשֶׁר נִמְצָא אִתּוֹ עֲצֵי שִׁטִּים, אֲשֶׁר יִמָּצֵא אִתּוֹ אֵין כְּתִיב כָּאן אֶלָּא אֲשֶׁר נִמְצָא אִתּוֹ. אָמַר רַבִּי לֵוִי מִמִּגְדַל צְבָעֲיָא קְצָצוּם וֶהֱבִיאוּם עִמָּהֶם לְמִצְרַיִם וְלֹא נִמְצָא בָהֶם לֹא קֶשֶׁר וְלֹא פֶקַע. אָעִין דְּשִׁטִּים הֲוָה בְּמִגְדְּלָא וְהָיוּ נוֹהֲגִים בָּהֶם אִסּוּר מִשּׁוּם קְדֻשַּׁת הָאָרוֹן, אֲתוֹן וְשָׁאֲלוּן לְרַבִּי חֲנִינָא חַבְרֵיהוֹן וְרַבָּנָן, אָמַר לָהֶם אַל תְּשַׁנּוּ מִמִּנְהַג אֲבוֹתֵיכֶם.