In order to assure that all property of the estate is placed in the custody of the trustee or the debtor-in-possession, anybody who holds property of the estate on the date of the filing must turn over the property to the debtor. A secured creditor (i.e., the Bank) who repossessed property before a bankruptcy petition was filed but who has not yet sold the collateral must return the collateral to the trustee or debtor-in-possession.