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 14:14-15
14
Then Yahweh said to me, The prophets prophesy lies in my name; I didn't send them, neither have I commanded them, neither spoke I to them: they prophesy to you a lying vision, and divination, and a thing of nothing, and the deceit of their own heart.
15
Therefore thus says Yahweh concerning the prophets who prophesy in my name, and I didn't send them, yet they say, Sword and famine shall not be in this land: By Sword and famine shall those prophets be consumed.
