The poem moves quickly from longing to violence and then to quiet. It opens with desire as something the speaker drinks, a "draft" taken in almost like a drug. Then the mood darkens. A gun brings "widowhood," and with it a whole "discourse of revenge," as if violence has its own language of meeting, dissolving, and handing out hurt. The poem doesn't say whose gun this is or what happened, so the scene stays shadowy and unsettling.
The last three lines change the tone. The speaker is "glad" to hear a sermon that is "too eloquent for a pulpit," and it turns out to be the rain, talking. After the harsh talk of revenge, the rain offers another kind of speech, one that is gentle and natural and needs no preacher. The speaker seems to find relief in it. The mood is tense at first, then calmer, with a hint that the natural world can soothe or outdo human cruelty.