Halakhah for Eruvin 101:4

(ידע ליה מר) א"ל לא ידענא ליה אמר ליה סמוך עלי דתניא ר' יוסי אומר אם היו שנים אחד מכיר ואחד שאינו מכיר זה שאינו מכיר מוסר שביתתו למכיר זה שמכיר אומר תהא שביתתנו במקום פלוני

or, as others read: 'under the palm-tree that releases it owner<span class="x" onmousemove="('comment',' By the abundance of its fruit and the proceeds derived from their sale.');">¹⁰</span> from the burden of taxes'.<span class="x" onmousemove="('comment',' Cur. edd. insert in parentheses, 'Does the Master know it?'');">¹¹</span> 'I do not know it', the other replied.' Rely then on me', the first said: it was taught: R'Jose ruled: If two were [travelling together] one of whom knew [of a well defined place] and the other did not know of it, the latter transfers his right to a choice of place to the former who then declare 'Let our Sabbath base be in such and such a place'.<span class="x" onmousemove="('comment',' Tosef. 'Er. III. Cf. supra 50b and notes.');">¹²</span>

Shulchan Arukh, Orach Chayim