Gift deed executed during pendency of mortgage

My father executed a registered gift deed of immovable property in favor of my younger brother in 2006. My father took a loan in 2005 by mortgaging this property with the bank and he was paying loan installments from the rent generated from this property till his death 2007. The property was mortgaged with the bank at the time of gift deed. Is this kind of gift deed valid OR not. Kindly provide Commentary or citations. Thanks