bet one's life / boots / bottom dollar

/bˈɛt wˈɒnz lˈaɪf bˈuːts bˈɒtəm dˈɒlə/

/bˈɛt wˈʌnz lˈaɪf bˈuːts bˈɑːɾəm dˈɑːlɚ/

to bet one's life / boots / bottom dollar

used to state one's certainty about something happening or being the case

Examples

1. I lost my umbrella, so you can bet your life that it's going to rain soon.

2. He hasn't passed us and we haven't passed him, but I'd bet my bottom dollar he's around somewhere.

3. You can bet your bottom dollar Sinclair was involved.

4. He talks about it a lot, but I would bet my bottom dollar that he has never actually been there.