Exode 25:5

and skins of rams dyed red, and purpled skins, and woods of sittin,

From a creature that was known in those days. As it is written, "and gave you sandals of tahash to wear (Ezek. 16:10)." Therefore, it was already known.

ועצי שטים, “and acacia wood.” Actually, the word שטים is a notrikon, an acrostic composed of the respective first letters in the words: שלום, טובה, ישועה, מחילה, “peace, goodness, salvation, and pardon.” There were some forests in the desert from which the Israelites were able to cut boards which they called shittim. This is also why we read in Joshua 2,1 that “Joshua sent out spies from (the forest around Shittim)” This is also what the prophet Isaiah referred to (Isaiah 41,19) when he wrote (in the name of the Lord) אתן במדבר ארז ,שיטה, והדס, “I will plant cedars in the deserts, acacias and myrtles, and oleasters.“ This is a very lightweight wood and it is very smooth. If we needed any proof that its wood was very light, consider the size of the boards of the Tabernacle’s which were 48 in number. Add two silver sockets for each board, i.e. 96 sockets, add all the upright boards use to surround the courtyard of the Tabernacle, which all had to be transported only by four wagons pulled by eight oxen, as spelled out in Numbers 4,29. Even though each board was 10 cubits high (6 meters) and their thickness was 1 cubit (60cm) and you will realise that unless the wood itself was extremely light, all of this could not have been pulled by only eight oxen. The other four oxen had to pull the weight of the carpets (4 layers) which formed the “roof” of the Tabernacle. We have been told in addition that the בריח התיכון, (Exodus 36,33), the center bolt, used to be Yaakov’s walking staff, the one with which he had crossed the river Jordan on his way to Lavan. Rashi claims that the shittim wood were trees that Yaakov had planted in Egypt as soon as he had come to Egypt, which the Israelites uprooted and took with them when departing from Egypt and which were used now to make the boards for the Tabernacle from. This is also what the liturgist bases himself on. Another interpretation found in the Midrash is that this was wood from the staff Yaakov had .taken with him on the way to Lavan. [I suppose that what the Midrash means is that Yaakov had planted that walking staff in the earth in Charan already, and it had developed. Ed.] This is why he had referred to it in Genesis 32,11, as a symbol of G–d’s providence guiding him during all the years he had been at Lavan. Ed.] It is not surprising therefore that he took those trees with him also to Egypt.