Article 1046 of Civil Code

The possessory pledge also terminates for any of the following reasons: a) If the pledgee relinquishes this right and has legal capacity to discharge the debtor from the debt. Relinquishment may be inferred implicitly from the creditor's voluntary surrender of the pledged thing. However, if the debt secured by the pledge is encumbered with a third party's right, the creditor's relinquishment shall not be effective against that third party unless he approves it. b) If the possessory pledge and ownership are united in the hands of one person. c) If the thing perishes or the pledged right expires.