Acacia wood is mentioned only in connection with the tabernacle (Exodus chapters 37 and 38). The following items were made of acacia wood: the ark and its poles, the table of showbread and its poles, the brazen altar and its poles, and the incense altar and its poles, all the poles for the hanging of the curtains as well as the supports [boards]. In short, all the structural features of the tabernacle were constructed of acacia wood.
The genus Acacia includes more than one hundred species of trees and shrubs which are found mainly in the arid and semiarid regions of Africa where they are ecologically the most important plants. Here the acacia trees are often the only plants on an otherwise bleak and monotonous terrain. Several species of acacia grow in the Sinai but not all would be suitable for use in construction. One of the most common is Acacia raddiana and it seems likely that this could be the acacia referred to in the Scriptures.
These trees are conspicuous in the desert with their often slanted, flat tops. The leaves are very small, an adaptation which helps the plant conserve water. In times of water stress, the tree can drop its leaves entirely. The flowers are white and borne in dense head-like clusters. The shape of the fruit varies in different species but in Acacia raddiana is a coiled pod-like structure which contains several very hard seeds.
Because of the slow growth of the tree, the wood is hard and dense. The heartwood is dark red-brown and attractive when polished. This wood is resistant to decay because the tree deposits in the heartwood many waste substances which are preservatives and render the wood unpalatable to insects making the wood dense and difficult to be penetrated by water and other decay agents.
Recent research on the weight of the wood used in the tabernacle system shows that solid boards would be extremely heavy. Therefore, it has been postulated that narrow pole-like structures were used (Zevit, Z. 1992. Timber for the tabernacle: Text, tradition, and realia. Eretz Israel 23: 136-143.) I have not seen large specimens of these trees in the Middle East. Perhaps such trees were present at the time of the wanderers in Sinai.
It is interesting to note that one of the freewill offerings which the children of Israel could bring for the tabernacle was acacia wood (Exodus 35:24). Those presenting an offering of silver or bronze brought it as an offering to the Lord, and everyone who had acacia wood for any part of the work brought it.
Uses of Acacia