Imagine a shopkeeper who, instead of actively seeking out potential customers (through advertising, marketing, etc.), sits in their shop waiting for someone to walk in or call. Clearly, they won't be as successful as someone who actively attracts customers.
In other words, there are two attitudes: one can wait to be called, or one can pick up the phone and call.
This new book of the Torah that begins this week is called Vayikra—He called. The previous book ends with the Divine commandment to build a Mishkan—a tabernacle for the Divine Presence. Moses then builds it, and the Glory of God fills the place. Now? God takes the initiative, calls Moses, and gives him a series of laws pertaining to ritual sacrifices.
After so much activity, the donations from the entire nation, the participation of hundreds in crafting every part of this magnificent building, the practical construction amidst the Israelite camps, the Glory of God manifested in a cloud filling the space of the Mishkan—does God really need to call Moshe to tell him something more? Moshe and the rest of the people should have asked for instructions themselves.
Perhaps we could say that God is teaching us something very simple and important: let's not be like the shopkeeper who opens a business and sits around waiting for someone to buy something; let's be proactive, pick up the phone and call. Let's not be content with just participating; let's call someone else to invite them to participate or simply call to see how they are, to say "I'm here" and make ourselves available.