Article 58 CISG
(1) If the buyer is not bound to pay the price at any other specific time, he must pay it when the seller places either the goods or documents controlling their disposition at the buyer's disposal in accordance with the contract and this Convention. The seller may make such payment a condition for handing over the goods or documents.
(2) If the contract involves carriage of the goods, the seller may dispatch the goods on terms whereby the goods, or documents controlling their disposition, will not be handed over to the buyer except against payment of the price.
(3) The buyer is not bound to pay the price until he has had an opportunity to examine the goods, unless the procedures for delivery or payment agreed upon by the parties are inconsistent with his having such an opportunity.