Hebrews 9:4 makes the strange claim that the golden altar of incense was part of the equipment of the Most Holy Place, the “second sanctuary” beyond the “second veil.” This seems to directly contradict the Torah, which says that Moses put the altar in front of the veil (Exodus 40:26). And it seems to contradict the import of Leviticus 16, which prohibits the high priest from passing through the veil on any day but the day of atonement.
But the author of Hebrews read more carefully than that, and he knew that the Torah also claims that the altar was set “before the ark of the testimony” (Exodus 40:5). Despite the veil separating altar and ark, Exodus and Hebrews both consider the two pieces of furniture together. We might even go a step further to suggest that the veil and the smoke of the incense are equivalent, since the high priest enters the Most Holy Place still “veiled” with smoke. Altar + smoke = ark + veil.
The combination ark-altar makes theological sense. The ark is Yahweh’s throne, and before the ark burns fragrant incense, the intercessions of King Yahweh’s priests and people. The veil/smoke is both a screen behind which Yahweh is hidden and a doorway by which Israel can approach.