Art. 52 CISG
(1) If the seller delivers the goods before the date fixed, the buyer may take delivery or refuse to take delivery.
(2) If the seller delivers a quantity of goods greater than that provided for in the contract, the buyer may take delivery or refuse to take delivery of the excess quantity. If the buyer takes delivery of all or part of the excess quantity, he must pay for it at the contract rate.
The Secretariat Commentary on Art. 48 of the 1978 New York Draft, predecessor to Art. 52 CISG, gives insight into the drafters' unterstanding on the eve of the 1980 Vienna Diplomatic Conference.
Overview of case law on Art. 52 CISG: UNCITRAL Digest
The UNCITRAL Digest on the CISG can be used as a starting point to discover the relevant case law on this article.