I am the Thief

I am the thief,
who comes in the night,
to steal your most precious treasures away,
but I won't steal your car,
and I won't steal your gold.
I won't even steal something valuably old.
Instead,
when you are fast asleep,
into your room I'll creep,
for I am the thief
and a thief will still something precious away.
But, what can this treasure be?
I am thief,
for I will steal a kiss
from your soft tender lips,
because you are the most precious thing that I see.