I have a contractual OBLIGATION...
The Big Bang Theory Season 6, Episode 1
As teacher, it's your OBLIGATION
to separate your personal idiosyncrasies...
The Big Bang Theory Season 1, Episode 17
...an inherent OBLIGATION
to maintain confidences?
The Big Bang Theory Season 2, Episode 1
...but you two
don't feel any OBLIGATION to join in.
The Big Bang Theory Season 1, Episode 4
You haven't given me a gift,
you've given me an OBLIGATION.
The Big Bang Theory Season 2, Episode 11