In the tabernacle of the congregation without the vail, which is before the testimony, Aaron and his sons shall order it from evening to morning before the LORD: it shall be a statute for ever unto their generations on the behalf of the children of Israel.

Jamieson-Fausset-Brown Bible Commentary

21. shall order it from evening to morning-The tabernacle having no windows, the lamps required to be lighted during the day. Josephus says that in his time only three were lighted; but his were degenerate times, and there is no Scripture authority for this limitation. But although the priests were obliged from necessity to light them by day, they might have let them go out at night had it not been for this express ordinance.

Matthew Henry's Concise Commentary

27:20,21 The pure oil signified the gifts and graces of the Spirit, which all believers receive from Christ, the good Olive, and without which our light cannot shine before men. The priests were to light the lamps, and tend them. It is the work of ministers, by preaching and expounding the Scriptures, which are as a lamp, to enlighten the church, God's tabernacle upon earth. Blessed be God, this light is not now confined to the Jewish tabernacle, but is a light to lighten the gentiles, and for salvation unto the ends of the earth.

Matthew Henry's Whole Bible Commentary

Verses 20-21

We read of the candlestick in the twenty-fifth chapter; here is an order given for the keeping of the lamps constantly burning in it, else it was useless; in every candlestick there should be a burning and shining light; candlesticks without candles are as wells without water or as clouds without rain. Now, 1. The people were to provide the oil; from them the Lord's ministers must have their maintenance. Or, rather, the pure oil signified the gifts and graces of the Spirit, which are communicated to all believers from Christ the good olive, of whose fulness we receive (Zec. 4:11, 12), and without which our light cannot shine before men. 2. The priests were to light the lamps, and to tend them; it was part of their daily service to cause the lamp to burn always, night and day; thus it is the work of ministers, by the preaching and expounding of the scriptures (which are as a lamp), to enlighten the church, God's tabernacle upon the earth, and to direct the spiritual priests in his service. This is to be a statute for ever, that the lamps of the word be lighted as duly as the incense of prayer and praise is offered.