That's a line from the movie Gosford Park, and it's the first line spoken by one of the upstairs characters. I have the habit of letting a movie like this play in the background over and over again while I write, and so, in this case, I've probably watched Gosford Park hundreds of times. Whenever I heard this line, I thought I had missed something someone said before it. After all, doesn't it feel like we've jumped into the middle of a conversation?
What I realized was that this line was, indeed, the first line of the scene, but it implied the bigger world. It suggested that someone else had told the speaker to "leave" something, whatever that something was.
Details have the power to make the world bigger without actually describing the bigger world. This line of dialog implied that there had been a conversation before it. We can assume that the normal, "Hi. How are you?" has taken place, but that the director, Robert Altman, decided it wasn't worth his time or ours to have to watch it.
When we're writing, we can do the same thing. As we describe an object or scene, we can use the details of that description to create the bigger world that exists around what readers are actually seeing.
He walked in wearing jeans and a T-shirt.
This line describes someone and their clothing, but with only a few more words, we can give this character a lot more history.
He walked in wearing mud-covered jeans and a torn T-shirt.
With this, we know that the person who came in has been alive long before we've heard about him. Maybe he's just been beat up. Made he's just a rough-and-tumble type of guy. Either way, our experience is now of something larger than what it was before. Our story takes on a grander scale.
We can come up with other examples like this, and they don't always have to imply that time has passed.
The light through the stained glass windows made the apple look blue.
Technically, here, I'm describing an apple, but I've also used the same sentence to imply a church or something like a church.
When I am writing a scene, I try to enlarge my imagination and see the bigger picture before I crop it down. If a character is entering the room, think about where they have come from and what they were doing there. If you're describing an object, think about where it is located and how that location affects it. Our world is larger than what we are able to write down, but with a few well-placed details, we can still capture some of that vastness.