To expand a bit, required reserves for commercial banks are calculated as a percentage of checkable deposits. Those reserves are required to be kept in the bank's account at the Fed. Excess reserves is anything above required reserves and that is the money used for the calculation to create loans.
Worth noting that the act of issuing a loan does indeed create money since an IOU from the borrower (bank's asset, not money) is balanced by the checkable deposit of the loan (bank's liability, actual money).
In any case, since the excess reserves exist on the asset side of the balance sheet, there probably isn't anything wrong with your statement that loans come from assets. Just a little more nuanced.