What could he be looking for in an empty house? What could he possibly need there in heaven? (4-5)
While death has already been announced in the title, the word "heaven" is the moment that it enters the poem itself. Taking the brother (who up until now we have taken to be alive, walking around upstairs) and suddenly revealing him to be dead mimics the shock and trauma of death. We have to readjust to the new reality the poem has created.
His love for me feels like spilled water running back to its vessel. (7-8)
As sad as it is, death is totally and completely irreversible, kind of like attempting to put water back into the glass that it spills from. But here, the impossible happens; the irreversible is reversed.
At this hour, what is dead is restless and what is living is burning. (9-10)
This refrain, which gets tweaked throughout, presents a sort of relationship between the dead and the living. By putting those two groups back-to-back, we can't help but feel that the restlessness of the dead (their presence in our speaker's mind) is causing the restlessness of the living, too – that feeling of "burning" that our speaker just can't shake.
At this hour, what is dead is helpless, kind and helpless. While the Lord lives. (29-30)
For the most part, people tend to think of God as immortal, everlasting. But here, our speaker talks about the Lord living. And if you can live, well, then you can die, right? To suggest that the Lord can die expands the scope of death, so that not even God is beyond it. Yikes.
with his mouth of teeth, a beard stained at feasts, and his breath of gasoline, airplane, human ash. (24-26)
Aside from being strange and menacing, the really striking thing about this description of God is that it presents Him as the jaws through which death is entered (and life is ended). Whoa. And, at least in this poem, death seems to be the most important act or aspect of God. Uplifting? Not so much.