In His Sermon on the Mount, Christ said, “Neither do men light a lamp to put it under a corn-measure, but on a stand, to give light to all that are in the house” (Mt 5:15). Let us hear how saints and sages have applied this teaching to their living according to the Word of God:
“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.” -St. Jerome
“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, as each one shall receive the things done in the body (2 Cor 5:10); 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.” -St. Augustine
“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. . . . The stand for the lamp is the Church which bears the word of life.” -Pseudo-Chrysostom
“Let none shut up his faith within the measure of the Law, but have recourse to the Church in which the grace of the sevenfold Spirit shines forth.” -St. Ambrose
“Christ Himself has lighted this lamp, when He filled the earthen vessel of human nature with the fire of His Divinity, which He would not either hide from them that believe, nor put under a bushel that is shut up under the measure of the Law, or confine within the limits of any one oration. The lampstand is the Church, on which He set the lamp.” -St. Bede the Venerable
St. Hilary of Poitiers states: “The lamp, that is, 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.'” St. Augustine adds that this “house” may be understood as either the Church or the world.
Quotations from St. Thomas Aquinas, Catena Aurea: Commentary on the Four Gospels Collected Out of the Works of the Fathers, Vol. I, Part I (Oxford: John Henry Parker, 1841).