I know the quality of the tobacco in it because I happen to own the plantation where it was grown, and I know therefore that when I light it, it will burn smoothly and pleasantly. I know above everything else that it will never explode in my face.

14 seconds sound clip from the Holiday (1938) movie soundboard.

You can hear this line at 00:37:59.387 in the Blu-ray version of the movie.

Quote context

[...]

- In marrying me, your mother and her family took not the slightest risk, either financially, or if I may say so, spiritually.

- Johnny will do well financially.

- No doubt about it. No doubt about it.

- From what Hobson tells me, that young man has great possibilities.

- Oh, I know it, Father.

- Then it's all right?

- Do you see that cigar?

- Yes, Father.

- That's a brand of cigar I've smoked for 35 years. Your grandfather smoked the same brand.

- I know the quality of the tobacco in it because I happen to own the plantation where it was grown, and I know therefore that when I light it, it will burn smoothly and pleasantly. I know above everything else that it will never explode in my face.

- And you're afraid that Johnny might?

- There's a strange new spirit at work in the world today, a spirit of revolt. I don't understand it, and I don't like it.

- Don't worry about Johnny, Father. I know him better than you.

- My dear, I've never denied you anything that was in my power to give.

[...]