1. Shulchan Aruch (CM 175:29): If Levi consulted with the neighbor (David), and David told him to buy it, David did not forfeit his rights. David can buy it from Levi, unless Levi acquired from him.
i. Beis Yosef (DH Ba): If he did not acquire, David can say 'I was joking, in order to establish the proper price. Had I asked to buy it, the seller would have charged more, for he knows that it is dear to me.' The Ran and Nimukei Yosef say that he must acquire, for we consider David to have a partial Kinyan in the land itself. However, Kinyan (Chalipin) suffices, even though it is like Kinyan of words,
2. Shulchan Aruch (ibid): Some say that it suffices if he said in front of witnesses 'you are witnesses against me that I withdrew.' He means that he withdrew properly with a Kinyan.
i. SMA (52 and Prishah 46): This is like other admissions in front of witnesses. He must mean that he withdrew with a Kinyan, for if not he has an excuse (I wanted you to buy it, lest the seller change me too much).
ii. Gra (71): This is like Odisa (an admission. It acquires, even if it is false), like R. Tam (Tosfos Bava Basra 44b DH d'Lo) and Siman 113:2.
3. Rema: If Levi told David to buy, and David said that he does not want to, some say that Levi acquired immediately. Levi does not become David's Shali'ach (to buy it for him) against David's will.
i. SMA (53): The Tur and Shulchan Aruch say that Kinyan is not needed when the seller asked the neighbor (and the neighbor told him to sell it. This implies that Kinyan is needed when the buyer asked the neighbor! The Mordechai says that waiving one's rights, and even Kinyan does not help. The Halachah does not follow him regarding this. Perhaps he would admit when the buyer offered to buy it in his own name and then give it to the neighbor, and the neighbor refused, for then he cannot say 'I wanted you to get it for the proper price.'
ii. Gra (72): This is like one who works another's field without the owner's knowledge. He is his Shali'ach, unless the owner objected.
iii. Shach (28): The Mordechai explains that the Gemara says 'he must acquire' to discuss after the buyer bought. Before the sale, saying 'go buy it' does not connote Bitul of the Shlichus. The Poskim are unlike the Mordechai, for they say (Sa'if 32) that after the sale a silent pardon suffices. If they held like the Mordechai, Kinyan would never help!
