write validation

app/models/validations/sales/financial_validations.rb

@@ -36,6 +36,10 @@ module Validations::Sales::FinancialValidations
     end
   end
 
+  def validate_mortgage(record)
+    record.errors.add :mortgage, I18n.t("validations.financial.mortgage") if record.mortgage == 0
+  end
+
   def validate_cash_discount(record)
     return unless record.cashdis