John Lightfoot on Matthew 10:27

[What ye hear in the ear.] We have observed before, that allusion is here made to the manner of the schools, where the doctor whispered, out of the chair, into the ear of the interpreter, and he with a loud voice repeated to the whole school that which was spoken in the ear.

"They said to Judah Bar Nachmani, the interpreter of Resh Lachish, Do you stand for his expositor." The Gloss is, "To tell out the exposition to the synagogue, which he shall whisper to you." We cannot here but repeat that which we produced before, The doctor whispered him in the ear in Hebrew. And we cannot but suspect that that custom in the church of Corinth which the apostle reproves, of speaking in the synagogue in an unknown tongue, were some footsteps of this custom.

We read of whispering in the ear done in another sense, namely, to a certain woman with child, which longed for the perfumed flesh; "Therefore Rabbis said, Go whisper her that it is the day of Expiation. They whispered to her, and she was whispered": that is, she was satisfied and at quiet.

[Preach ye upon the housetops.] Perhaps allusion is made to that custom when the minister of the synagogue on the sabbath-eve sounded with a trumpet six times upon the roof of an exceeding high house, that thence all might have notice of the coming in of the sabbath. The first sound was, that they should cease from their works in the fields; the second, that they should cease from theirs in the city; the third, that they should light the sabbath candle, &c.