As the speaker's lady attempts to kill the flea, he stops her, asking to show mercy for inside the flea there are three lives: his own, his lady's and the flea's. To kill the flea would not only end the flea's live but would also be impertinent "three sins in killing three." Within the flea the union of their blood consummates them basically to marriage "where we almost, yea, more than married are." The union inside of the flea is their home and their life together "our marriage bed, and marriage temple is." The lady's parents resent her relationship with the speaker even though they know that she has chosen not to engage in premarital sex with the speaker. .
The speaker supports his main idea by referring to the ceremony of marriage which signifies that a man and women shall be united together to be come one flesh. He makes a case using the combination of their blood which is symbolic of life and soul, which has become one flesh and now they are married. This is where the flea becomes a marriage sanctuary. This union not only helps to strengthen his sexual plea but also supplies him with a strong influence to help defend him when his lady does what any rational woman would do; she attempts to kill the flea. Here Donne expresses the fact that by squashing the flea she is spreading the speaker's blood and hers as well, basically carrying out the act of murder. The lady is not only ending this extraordinary flea's life but breaking the holy bond of marriage as well. Death in this situation not only ends the lives of the flea, the speaker and the lady but also refers to an even more holy trinity image: the father, the son and the Holy Spirit. The speaker pleads for his lady not to kill the flea because the flea's death is symbolically to showing the end of sex or an orgasm . In the era when this poem was written, people believed that every time a man engaged in intercourse his life was reduced .