Please give an explanation of the following quote from "A Refusal To Mourn the Death, by Fire, of a Child in London."
And I must enter again the round
Zion of the water bead
And the synagogue of the ear of corn
Shall I let pray the shadow of a sound
Or sow my salt seed
In the least valley of sackcloth to mourn
This excellent poem by Thomas represents his defiance of the traditional means of accepting death, and is notable for the way that it reveals more about the speaker and his own beliefs than we are ever told about the child whose death triggers off this rumination about mortality.
The second stanza, which you have quoted, refers to the speaker's belief in the way that, when we die, our life diffuses into a kind of universal life. Thus it is that when we die we must "enter again" the "Zion of the water bead" and the "synagogue of the ear of corn." Note the way that Thomas infuses these examples of nature with religion, using a metaphor to compare them to places of worship of of religious significance. Death, therefore, is no more than a return to nature, a means of transforming our selves into becoming incorporated with nature and life in a different way.
Only when this process occurs to the speaker will he then feel free to mourn, as only then will he be able to write about or express the experience of the child in death and how this child came to become more a part of nature in his death than he ever did in its life. Thus this stanza refers to the belief of the poet with regard to what happens with us when we die, and how we become more alive in our deaths than we do in our life.