Responsa for Bava Batra 312:10

רבי יהושע

IN [RESPECT OF] THE SABBATH<span class="x" onmousemove="('comment',' When these are forbidden, and the rule, 'whenever something is suitable for fusion, actual fusion is not essential', cannot be applied. ');">²⁸</span> HOW MUCH MORE SO IN [THE CASE OF] A WEEK-DAY?<span class="x" onmousemove="('comment',' When writing and acquisition are permissible and possible, and the rule, 'Whenever something is suitable etc.' (V. previous note) may be applied. ');">²⁹</span> SIMILARLY: ONE MAY ACQUIRE OWNERSHIP ON BEHALF OF A MINOR<span class="x" onmousemove="('comment',' Because he himself is not legally entitled to acquire possessions. ');">³⁰</span> BUT NOT ON BEHALF OF [A PERSON WHO IS] OF AGE,<span class="x" onmousemove="('comment',' Since he is himself able to acquire possession. ');">³¹</span> THESE ARE THE WORDS OF R. ELIEZER. R. JOSHUA SAID: [IF THEY ALLOWED POSSESSION<span class="x" onmousemove="('comment',' In his absence. ');">³²</span> TO BE ACQUIRED] ON BEHALF OF A MINOR,<span class="x" onmousemove="('comment',' Who cannot himself acquire. ');">³³</span> HOW MUCH MORE SO ON BEHALF OF [A PERSON WHO IS] OF AGE.<span class="x" onmousemove="('comment',' Since he himself is entitled to acquire and be may also appoint an agent to act on his behalf, others also, much more than in the case of a minor, are entitled to acquire possession for him in his absence. ');">³⁴</span> <b><i>GEMARA</i></b>. Whose [version is represented in] our Mishnah? — It [is that of] R. Judah. For it was taught: R. Meir stated, 'R. Eliezer said: On a week-day his [verbal] instructions<span class="x" onmousemove="('comment',' V. supra p. 681, n. 7. ');">³⁵</span> are legally valid because he is able to write,<span class="x" onmousemove="('comment',' And the rule, 'Whenever fusion is possible. actual fusion is not essential', can be applied. Since writing and acquisition are possible on a week-day, actual writing and acquisition are not indispensable. ');">³⁶</span> but not on the Sabbath.<span class="x" onmousemove="('comment',' V. supra p. 681, n. 11. ');">³⁷</span> R. Joshua

Teshuvot Maharam