Exodus 30:1

And thou shalt make an altar to burn incense upon
The Targums of Onkelos and Jonathan call it incense of spices, properly enough, for it was made of various spices; of which see ( Exodus 30:34 ) and this was necessary on a natural and civil account, to remove those ill smells from the sanctuary, occasioned by the number of beasts continually slain in it; but chiefly on a religions account, to denote the acceptableness of the service of the sanctuary to God:

of shittim wood shall thou make it:
of the same that the altar of burnt offering was made, which was covered with brass, but this with gold, as after related; of this sort of wood, (See Gill on Exodus 25:5) as this altar was a type of Christ, the shittim wood may respect his human nature; which wood, though it sprung out of the earth, was not common, but choice and excellent, and very strong durable, and incorruptible; and so Christ, though he was man made of an earthly woman in his human nature, yet was chosen out of the people, is the chiefest among ten thousand, and excellent as the cedars, the man of God's right hand, whom he made strong for himself; and though he died in it, he saw no corruption, he now lives, and will live for evermore; in which nature he acts the part of a Mediator, and intercedes for his people, and offers up their prayers, perfumed with the much incense of his mediation, to which this altar has a special respect.