Shevuot 48B

שהבן גובה בין בשבועה ובין שלא בשבועה, והאב אינו גובה אלא בשבועה. היכי דמי ⁠– דמת לוה בחיי מלוה;

as the son can collect both by taking an oath and without taking an oath, while the father can collect only by taking an oath. What are the circumstances in which this occurs? It is when the borrower died during the life of the lender. The father who is the lender can collect from the borrower’s heirs only if he takes an oath.

וקתני: שהבן גובה בין בשבועה ובין שלא בשבועה; בשבועה ⁠– שבועת יורשין, שלא בשבועה ⁠– כרבן שמעון בן גמליאל!

And it is taught: As the son can collect both by taking an oath and without taking an oath. He collects by taking an oath when he takes the heirs’ oath, that he has no knowledge that his father’s debt was paid, and he collects without taking an oath in accordance with the opinion of Rabban Shimon ben Gamliel in the Mishnah, that when there are witnesses that the father said at the time of his death that a certain promissory note had not been paid, the son collects the debt without taking an oath. In any case, absent testimony to that effect, the father bequeaths the oath to his children and the son can collect by taking an oath, contrary to the ruling of Rav and Shmuel.

אמר רב יוסף: הא מני ⁠– בית שמאי היא, דאמרי: שטר העומד לגבות ⁠– כגבוי דמי.

Rav Yosef said in response: In accordance with whose opinion is this baraita? It is in accordance with the opinion of Beit Shammai, who say that a debt recorded in a promissory note that stands to be collected is considered as if it is already collected. Therefore, the father is considered to be already in possession of the loan and bequeaths it to his son. Even though the rabbis instituted that the son take an oath to the heirs of the borrower, this is not a case of the son inheriting an oath.