If I should die, think only this of me:
That there's some corner of a foreign field
That is for ever England.  There shall be
In that rich earth a richer dust concealed;
A dust whom England bore, shaped, made aware,
Gave, once, her flowers to love, her ways to roam,
A body of England's, breathing English air,
Washed by the rivers, blest by suns of home.
And think, this heart, all evil shed away,
A pulse in the eternal mind, no less
Gives somewhere back the thoughts by England given;
Her sights and sounds; dreams happy as her day;
Note that this poem is a sonnet. The  volta  or ‘turn’ could be said to be at this point, dividing the first eight lines on thoughts of death from the last six lines which hark back to England and the joy that the poet derives from his country. 
 In dying for his country, the soldier has sacrificed himself, become a martyr for England. Brooke suggests that his heart (perhaps soul) has been purified by this sacrifice, in a manner reminiscent of the  baptism of blood , and hence has no longer any trace of sin.
The Soldier