Update date field based on lead history using anonymous apex

anon.apex

Lead[] leads = [
    select Id,
    (select Id, Field, OldValue, NewValue, CreatedDate from Histories order by CreatedDate asc)
    from Lead
    where Status='Closed'
	and Closed_Date__c = null
    order by LastModifiedDate asc
    limit 1000
];
Lead[] toUpdate = new Lead[]{};
for (Lead l : leads) {
    for (LeadHistory lh : l.Histories) {
        System.debug('****** ' + lh);
        if (lh.Field == 'Status' && lh.NewValue == 'Closed') {
            l.Closed_Date__c = Date.valueOf(lh.CreatedDate);
            toUpdate.add(
                new Lead(
                    Id = l.Id,
                    Closed_Date__c=Date.valueOf(lh.CreatedDate)
                )
            );
        }
    }
}
System.debug(toUpdate);