Responsa for Bava Batra 292:4

<big><strong>גמ׳</strong></big> מאן תנא דאזלינן בתר אומדנא אמר רב נחמן רבי שמעון בן מנסיא היא דתניא הרי שהלך בנו למדינת הים ושמע שמת בנו ועמד וכתב כל נכסיו לאחר ואחר כך בא בנו מתנתו מתנה רבי שמעון בן מנסיא אומר אין מתנתו מתנה (שאלמלא) היה יודע שבנו קיים לא היה כותבן

[IF, HOWEVER,] HE DID NOT LEAVE [FOR HIMSELF] SOME [PIECE OF] LAND, HIS GIFT IS INVALID<span class="x" onmousemove="('comment',' If he recovered. Since he left nothing for himself it is obvious that at the time he made the gift he did not expect to live any longer. Had he hoped to recover from his illness he would not have given away all his landed property, leaving himself destitute. ');">¹³</span> <b><i>GEMARA</i></b>. Who is the Tanna [that holds the view] that the assumed motive<span class="x" onmousemove="('comment',' [H] lit., assumption'. 'estimation'. ');">¹⁴</span> is a determining factor?<span class="x" onmousemove="('comment',' Lit., 'that we go after assumption', i.e., that the assumed motives and intentions of a testator are to be taken into consideration when deciding the legality of his 'statements In our Mishnah, the assumed motive and intention are obviously the determining factors (V., notes 3, 4); who is its author? ');">¹⁵</span> — R. Nahman replied: It [is the view of] R. Simeon b. Menasya. For it was taught: In the case of [a person] whose son went to a distant country<span class="x" onmousemove="('comment',' Lit., 'country of (i.e., beyond) the sea'. ');">¹⁶</span>

Teshuvot Maharam