Responsa for Bava Batra 59:3

Q. When A demanded of B the return of the money he had given him, B repaid part of it and provided A with a surety for the rest. The fact that B provided A with a surety is attested to by witnesses. Now, however, B claims that this money was originally given to him by A not as a loan but as an outright gift, that consequently he owes nothing to A, and that when he provided A with a surety he acted "inside the line of justice."
A. The testimony of the witnesses to the effect that B provided A with a surety, is convincing proof that A had given the money to B as a loan. Although a person will sometimes buy what by law belongs to him in order to avoid litigation, this principle applies only when the rightful owner is not in possession of the disputed property, while in our case B was in possession of the money. Moreover, even if there were no such witnesses, we would have put no credence in B's assertion that he provided A with a surety only because he acted "inside the line of justice." For the principle of Miggo — that we ought to believe B's present statement since, were he inclined to lie, he could have denied altogether having provided A with a surety — does not apply to this case, since we are thoroughly convinced that had B not owed the money to A, he would not have repaid part of it.
SOURCES: Cr. 166; Am II, 164.

Q. A, a widow's trustee, leased half of the widow's house, for a term of ten years, to C, who, in turn, leased it to B. After B moved into the house, A became greatly dissatisfied with him and demanded that B move out of the house immediately, on the ground that he had leased the house to C, and therefore was under no obligation to B. He told B, however, that should C have any claims against him on account of the eviction of B, he, A, would answer these charges in court. B, however, claimed: that C rented the house from A on condition that he (C) lease it to whomever he wants; that he, B, was willing to partition off the part of the house he occupies from the rest of the house; and that he would guarantee to pay the widow for any damages she may sustain as a result of his remaining on the premises. A, however, claimed that he feared that grave damages to the widow will result if B stays, and that the widow cannot dwell in one house with a snake (meaning B).
A. Since A admits that C had the right to lease the house to anyone he pleased, A cannot evict B from the widow's house.
SOURCES: Cr. 259; Pr. 680; Mord. B. M. 357; Agudah B. M. 125. Cf. Hag. Maim. to Sekirut 5, 20; Weil, Responsa 10.