Bava Batra 42A

אינהו אפסידו אנפשייהו.

they caused their own loss by not investigating whether there was a lien on the property that they intended to buy.

ומי אמר רב הכי? והתנן: המלוה את חבירו בשטר ⁠– גובה מנכסים משועבדים, על ידי עדים ⁠– גובה מנכסים בני חורין!

The Talmud asks: And did Rav, in fact, say this, that one can collect sold property by means of witnesses alone? But didn’t we learn in a Mishnah (175a): One who lends money to another with a promissory note collects his debt from liened property that had been sold after the loan, if the debtor has no other property; but if one lent by means of witnesses without a promissory note, he collects his debt only from unsold property?

וכי תימא: רב תנא הוא ופליג, והא רב ושמואל דאמרי תרוייהו: מלוה על פה ⁠– אינו גובה לא מן היורשים ולא מן הלקוחות!

And if you would say that Rav is a tanna, and as such has the authority to dispute the determination in the Mishnah, but didn’t Rav himself and Shmuel both say: One who is owed a debt due to a loan by oral contract does not collect liened property, not from the heirs of the debtor nor from the buyers, despite the fact that there are witnesses?

מלוה אזביני קא רמית?! מלוה, כי קא יזיף ⁠– בצנעא קא יזיף, כי היכי דלא ליתזלו נכסיה עליה. זביני, מאן דזבין ארעא ⁠– בפרהסיא זבין, כי היכי דליפוק לה קלא.

The Talmud answers: Are you raising a contradiction from a case of a loan to a case of a sale? They are not comparable. In the case of a loan, when one borrows money he borrows discreetly, in order that his property not be devalued, as people will pay less for his property if they know that he is pressed for capital. Since a loan is issued discreetly, the presumption is that the buyers were unaware of the loan. Therefore, the creditor does not collect from sold property. By contrast, in the case of a sale, one who sells land sells it in public in order that publicity be generated with regard to it. Therefore, the cases of loans and sales are not comparable.