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 36:29-30
29
Concerning Jehoiakim king of Judah you shall say, Thus says Yahweh: You have burned this scroll, saying, Why have you written therein, saying, The king of Babylon shall certainly come and destroy this land, and shall cause to cease from there man and animal?
30
Therefore thus says Yahweh concerning Jehoiakim king of Judah: He shall have none to sit on the throne of David; and his dead body shall be cast out in the day to the heat, and in the night to the frost.
