P.R. Laws tit. 31, § 5121 : ONE Civil Code —Subtitle 4 Obligations and Contracts —PART XVI. Obligations Contracted Without Agreement —Chapter 391. Quasi Contracts —Subchapter II. Collection of What is Not Due —§ 5121. Restitution of thing improperly received TEXT PDF If a thing is received when there was no right to claim it and which, through an error, has been unduly delivered, there arises an obligation to restore the same. History —Civil Code, 1930, § 1795.