בְּאֹ֣הֶל מוֹעֵד֩ מִח֨וּץ לַפָּרֹ֜כֶת אֲשֶׁ֣ר עַל־הָעֵדֻ֗ת יַעֲרֹךְ֩ אֹת֨וֹ אַהֲרֹ֧ן וּבָנָ֛יו מֵעֶ֥רֶב עַד־בֹּ֖קֶר לִפְנֵ֣י יְהוָ֑ה חֻקַּ֤ת עוֹלָם֙ לְדֹ֣רֹתָ֔ם מֵאֵ֖ת בְּנֵ֥י יִשְׂרָאֵֽל׃ (ס)
In the tent of meeting, without the veil which is before the testimony, Aaron and his sons shall set it in order, to burn from evening to morning before the LORD; it shall be a statute for ever throughout their generations on the behalf of the children of Israel.
Read kabbalistic (mystical) interpretation of Exodus 27:21: and classical mystical sources.