50 Grk “what you hear in the ear,” an idiom.
51 The expression “proclaim from the housetops” is an idiom for proclaiming something publicly (L&N 7.51). Roofs of many first century Jewish houses in Judea and Galilee were flat and had access either from outside or from within the house. Something shouted from atop a house would be heard by everyone in the street below.

In other versions

What I tell you in the dark, say in the light, and what you hear whispered, proclaim on the housetops.

What I tell you in the dark, speak in the daylight; what is whispered in your ear, proclaim from the roofs.

What I tell you in the dark, speak in the light. What you hear in a whisper, proclaim on the housetops.

What I tell you now in the darkness, shout abroad when daybreak comes. What I whisper in your ear, shout from the housetops for all to hear!

What I say to you in the dark, tell in the light, and what you hear in your ear, proclaim on the housetops.

What I tell you in darkness, that speak ye in light: and what ye hear in the ear, that preach ye upon the housetops.

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