John Donne's "Death, be not proud," or Holy Sonnet 10, is a poem written in the form of an Italian sonnet. It is narrated in the first person. The narrator directly addresses Death, a figure personified in the poem. The concept of eternity is mentioned in the poem's last two lines.
One short sleep past, we wake eternally
And death shall be no more; Death, thou shalt die.
The key to understanding the meaning of eternity in this poem is to know that Donne, born into a Roman Catholic family, converted to Anglicanism and was, in 1615, ordained as a priest in the Church of England. This means he is writing not just as a Christian, but as a theologically knowledgeable cleric, and distinguished preacher whose sermons are still widely read.
Donne's concept of eternity assumes the immortality of the soul. He points out that although our body dies, our souls live on eternally (either in Heaven or Hell); thus, the triumph of death is only apparent and temporary, affecting our physical rather than spiritual selves.
In Christian theology, death itself is only temporary and will no longer exist after the Last Judgement. Paradoxically, while human souls live on forever, according to Christian theology, death itself "dies" or ceases to exist permanently.