Article 70 of the Patent Law: Anyone who uses, promises to sell or sells an infringing patented product for the purpose of production and operation without knowing that the product was manufactured or sold without the permission of the patentee shall not be liable for compensation.
No proof of sales is required before the application date. Even if he authorizes you to start selling, as long as you can prove that the source of the product is legal, it is infringement, but there is no compensation.