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 23:5-6
5
Behold, the days come, says Yahweh, that I will raise to David a righteous Branch, and he shall reign as king and deal wisely, and shall execute justice and righteousness in the land.
6
In his days Judah shall be saved, and Israel shall dwell safely; and this is his name by which he shall be called: Yahweh our righteousness.