If this be error and upon me proved,

I never writ, nor no man ever loved.
These lines are an example of a/an

rhyming couplet

http://encyclopedia.farlex.com/Rhyming+couplets

These lines are an example of a couplet, which is a pair of consecutive lines in a poem that often rhyme. In this case, the couplet is from William Shakespeare's Sonnet 116.