God directs Jeremiah to deliver a critical prophetic message in the most public and central location available. By standing in the courtyard of the Temple, the prophet is positioned in the one unifying center where individuals representing every class and background gather [ביאור שטיינזלץ]. Commentators agree that the directive to address the cities of Judah is not aimed at the physical locations themselves, but rather at the residents of those towns who have traveled to the Temple to worship.
Along with choosing this specific location, God gives a strict instruction to deliver His prophecy exactly as received, without holding back a single word. This warning is especially necessary given the nature of the audience. Because the prophet is speaking to a large, mixed crowd, the message will likely be unpopular and difficult for them to hear. Despite any temptation to soften the blow, he must present the message completely and accurately, without the slightest omission [ביאור שטיינזלץ].