
I SWEAR it by the Old Gods and New.
Game of Thrones Season 3, Episode 9

perhaps you should start
a SWEAR jar.
The Big Bang Theory Season 7, Episode 10

Walt, I SWEAR I didn't.
Breaking Bad Season 5, Episode 10

Okay.
No one else knows, I SWEAR!
Breaking Bad Season 5, Episode 14

I SWEAR it.
Game of Thrones Season 3, Episode 8