Responsa על בבא בתרא 71:11

R. Asher disagrees with R. Hayyim Eliezer, and maintains that the rule of Asmakta is not applicable in this case. B is considered the agent of A, since the latter voiced no protest when B bound himself, in the presence of A to reconcile C for damages, in the event of a breach of promise. Under these arrangements, the sale was then completed, and the fulfillment of the terms rested with A.