15 Neither do men light a candle and put it under a bushel, but upon a candlestick, that it may shine to all that are in the house.
Jerome: He instructs them what should be the boldness of their preaching, that as Apostles they should not be hidden through fear, like lamps under a corn-measure, but should stand forth with all confidence, and what they have heard in the secret chambers, that declare upon the house tops.
Pseudo-Chrysostom: The lamp is the Divine word, of which it is said, “Thy word is a lamp unto my feet” [Ps 119:105]. They who light this lamp are the Father, the Son, and the Holy Spirit.
Augustine: Putting the lamp under the corn-measure means the preferring bodily ease and enjoyment to the duty of preaching the Gospel, and hiding the light of good teaching under temporal gratification. The corn-measure aptly denotes the things of the body, whether because our reward shall be measured out to us [2 Cor 5:10], as each one shall receive the things done in the body; or because worldly goods which pertain to the body come and go within a certain measure of time, which is signified by the corn-measure, whereas things eternal and spiritual are contained within no such limit.
He places his lamp upon a stand, who subdues his body to the ministry of the word, setting the preaching of the truth highest, and subjecting the body beneath it. For the body itself serves to make doctrine shine more clear, while the voice and other motions of the body in good works serve to recommend it to them that learn.
Pseudo-Chrysostom: Men of the world may be figured in the “corn-measure” as these are empty above, but full beneath, so worldly men are foolish in spiritual things, but wise in earthly things, and therefore like a corn-measure they keep the word of God hid, whenever for any worldly cause he had not dared to proclaim the word openly, and the truth of the faith. The stand for the lamp is the Church which bears the word of life, and all ecclesiastical persons.
Hilary: The lamp, i.e. Christ Himself, is set on its stand when He was suspended on the Cross in His passion, to give light for ever to those that dwell in the Church; “to give light,” He says, “to all that are in the house.”
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).