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.
Ezekiel 5:11-12
11
Therefore, as I live, says the Lord Yahweh, surely, because you have defiled my sanctuary with all your detestable things, and with all your abominations, therefore will I also diminish [you]; neither shall my eye spare, and I also will have no pity.
12
A third part of you shall die with the pestilence, and with famine shall they be consumed in the midst of you; and a third part shall fall by the sword around you; and a third part I will scatter to all the winds, and will draw out a sword after them.