Speak
Like "say," the word "speak" refers to thoughts and feelings moving from our more internal spiritual levels to our more external ones -- and ultimately from the Lord, who is in a sense the most internal spiritual level of all. This is generally called "influx" and "perception" in the Writings, meaning they are thoughts and feelings that flow in in a complete way from the Lord, rather than being things we have to think about and figure out. On a number of occasions "speak" and "say" are used together; in these cases "speak" refers more to intellectual instruction in matters of thought and "say" refers more to feelings and affections that flow in directly.
Jeremiah 49:34-39
34
The word of Yahweh that came to Jeremiah the prophet concerning Elam, in the beginning of the reign of Zedekiah king of Judah, saying,
35
Thus says Yahweh of Armies: Behold, I will break the bow of Elam, the chief of their might.
36
On Elam will I bring the four winds from the four quarters of the sky, and will scatter them toward all those winds; and there shall be no nation where the outcasts of Elam shall not come.
37
I will cause Elam to be dismayed before their enemies, and before those who seek their life; and I will bring evil on them, even my fierce anger, says Yahweh; and I will send the sword after them, until I have consumed them;
38
and I will set my throne in Elam, and will destroy from there king and princes, says Yahweh.
39
But it shall happen in the latter days, that I will bring back the captivity of Elam, says Yahweh.