It's only a matter of minutes.
4 seconds sound clip from the Night of the Living Dead (1968) movie soundboard.
You can hear this line at 01:02:18 in the Blu-ray version of the movie.
Quote context
[...]
- I heard.
- I'll come back down as soon as I find out what they want.
- The bodies should be disposed of at once, preferably by cremation.
- Well, how long after death, then, does the body become reactivated?
- It's only a matter of minutes.
- Minutes? Well, that doesn't give people time to make any arrangements.
- No, you're right. It doesn't give them time to make funeral arrangements.
- The bodies must be carried to the street and... and burned.
- They must be burned immediately. Soak them with gasoline and burn them.
- The bereaved will have to forgo the dubious comforts that a funeral service will give.
[...]