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 7:19-21
19
Do they provoke me to anger? says Yahweh; [do they] not [provoke] themselves, to the confusion of their own faces?
20
Therefore thus says the Lord Yahweh: Behold, my anger and my wrath shall be poured out on this place, on man, and on animal, and on the trees of the field, and on the fruit of the ground; and it shall burn, and shall not be quenched.
21
Thus says Yahweh of Armies, the God of Israel: Add your burnt offerings to your sacrifices, and eat meat.
