The parallel passage, Luke 12:3, is verbally similar, but of reverse meaning. In Matthew it is a charge to the disciples to proclaim publicly what Christ tells them privately; in Luke it is a statement that what they say privately shall be proclaimed publicly.
St. Luke gives only another side of the preceding verse; St. Matthew, a fresh point. The connexion with verse 26 is—Do not cover up your relation to me, but say out bravely the message that I give you.
What I tell you. There is no limitation to the time. Those who believe in the present life of Christ and in the reality of present communications from him cannot fail to see here both the true source of their messages as preachers and the necessity of faithfulness to those messages.
Observe that the stress is not upon the personality of the Speaker, but upon the communication ( λέγω, not ἐγὼ λέγω). In (the, Revised Version) darkness … in (the, Revised Version) light. Both are pictured to the mind.
And what ye hear in the ear ( εἰς τὸ οὖς). Possibly a reference to the habit of Jewish rabbis sometimes whispering their teaching in the ear of an "interpreter," who repeated it aloud for all to hear (cf.
Lightfoot, 'Hor. Hebr.'), but more probably only the common figure of speech for secret instruction; cf. Talm. Bab., 'Berach.,' 22a, "Nahum of Gamzo, whispered it to. R. Akiba, and R. Akiba whispered it to Ben Azai, and Ben Azai went out and taught it to his disciples in the street."
Compare also the Old Testament phrase, "uncover the ear" (1 Samuel 9:15, used of God; 1 Samuel 20:2,1 Samuel 20:12, 1 Samuel 20:13, used of man). That preach ye; proclaim (Revised Version); κηρύξατε.
Upon the house-tops. Lightfoot ('Hor. Hebr.') thinks that this is an allusion to the minister of a synagogue blowing a trumpet on the roof of a high house to announce the sabbath; but that was a mere signal of a fact ( σαλπίζω), not the articulate expression of a communication ( κηρύσσω).
The phrase much more probably alludes to the fact that the roofs in Eastern cities are the common place for conversation, and to the rapidity with which an announcement there made spreads throughout the town.