As Pam said, the standard CAR Listing agreement, which I assume you signed, says that if the listing agent provides you (within X days of listing expiration) with names of the persons who have viewed the house and/or made offer on the house during the listing period, then they will be entitled to the listing side of the commission if those named persons made an offer within in an agreed upon timeframe (again, that's in the contract you signed) after the listing expires.
The reason is because those buyers were introduced to your house while the house was listed under the agent, so it provides protection for the listing agent who have spent the time/money/energy to advertise and market your home.
Your agent would have explained that to you before the listing agreement was signed. .
You will need to provide those names to your new listing agent BEFORE any new listing agreement is signed so the new agent is aware of the exclusion and add that to the new listing agreement so everything is spelled out. .
This is a standard clause in CAR listing agreement and should have been signed when you signed the listing agreement.
You need to go back to your original listiing agreement and see what you agreed as the specific number of days. That's what is binding.