In Celebration of My Third Poem by Donne

"What I will say, I will not tell thee now, / Lest that preserve thee" ("The Apparition," 14-15).

In deducing the connotative situation of this poem, I'm zeroing in on lines like "thou thinkst thee free / From all solicitation from me" (2-3) and "in worse arms shall see" (5). The speaker claims that his "murderess," likely a former lover ("my love is spent," line 15), isn't off the hook. She will receive some sort of persistent request from the speaker, and I don't think it's a nice one. The speaker seems to imply that his "murderess" cheated on him -- that's why I think he wants her to "painfully repent" (16). I split that infinitive in service of the quote's cohesion.

So I'm going to analyze my quoted line based on that situation.

What is the speaker going to say to her? It's an empty threat. However, empty threats can be the most powerful ones. When we threaten people like that, they usually assume the worst. I don't think the speaker actually has a plan as to what he's going to say to his "murderess," or even if he's going to say anything to her at all, but if he does, I know it can't be good. The tone throughout the poem is very judgmental of the woman in question, and this quote extends the tone to threatening, as well.