Alexander Sergeyevich Pushkin - Thou and You

She substituted, by a chance,
For empty 'you' - the gentle 'thou';
And all my happy dreams, at once,
In loving heart again resound.
In bliss and silence do I stay,
Unable to maintain my role:
'Oh, how sweet you are!' I say -
'How I love thee!' says my soul.

Alexander Sergeyevich Pushkin

http://www.poemhunter.com/poem/thou-and-you-2/