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 25:27-29
27
You shall tell them, Thus says Yahweh of Armies, the God of Israel: Drink, and be drunk, vomit, fall, and rise no more, because of the sword which I will send among you.
28
It shall be, if they refuse to take the cup at your hand to drink, then you shall tell them, Thus says Yahweh of Armies: You shall surely drink.
29
For, behold, I begin to work evil at the city which is called by my name; and should you be utterly unpunished? You shall not be unpunished; for I will call for a sword on all the inhabitants of the earth, says Yahweh of Armies.
