It means that this is beginning.
2 seconds sound clip from the Se7en (1995) movie soundboard.
You can hear this line at 00:23:35.682 in the Blu-ray version of the movie.
Quote context
[...]
- Set them on the desk, please.
- They were, uh... They were fed to him.
- This was found on the wall behind the refrigerator in the obesity murder scene.
- Long is the way and hard that out of hell leads up to light.
- It's from Milton. Paradise Lost.
- It means that this is beginning.
- This was found behind the same refrigerator. Written in grease.
- There are seven deadly sins, captain: Gluttony, greed, sloth, wrath, pride, lust and envy. Seven.
- Hold on. This is not even my desk.
- You can expect five more of these.
[...]