Adam Clarke on Exodus 30:1

Altar to burn incense - The Samaritan omits the ten first verses of this chapter, because it inserts them after Exo 26:32 (note).

Shittim wood - The same of which the preceding articles were made, because it was abundant in those parts, and because it was very durable; hence everywhere the Septuagint translation, which was made in Egypt, renders the original by ξυλον ασηπτον, incorruptible wood.