JULIET:Although I joy in thee,
I have no joy of this contract tonight.
It is too rash, too unadvised, too sudden,
Too like the lightning, which doth cease to be
Ere one can say “It lightens.”

William Shakespeare (1564-1616) English dramatist and poet

Romeo and Juliet, Act 2, sc. 2, l. 123ff (2.2.123-127) (1595)
    (Source)

On Romeo swearing his love to her.