Charles Ellicott Commentary Exodus 27:21

"In the tent of meeting, without the veil which is before the testimony, Aaron and his sons shall keep it in order from evening to morning before Jehovah: it shall be a statue for ever throughout their generations on the behalf of the children of Israel." — Exodus 27:21 (ASV)

In the tabernacle of the congregation. —Hebrew, in the tent of meeting — that is, the place where God met the earthly ruler of His people. .

Before the testimony — that is, in front of the Ark which contained “the Testimony,” or “Two Tables.” (See Note on Exodus 16:34).

Aaron and his sons. —The priestly character of Aaron and his descendants, laid down in the next chapter, is here anticipated.

From evening to morning. —See the second Note on Exodus 27:20).