Halakhah for Eruvin 101:15

א"ר אחא בר יעקב המעביר ד"א ברה"ר אינו חייב עד שמעביר הן ואלכסונן

If, however, he does not uphold the word analogy<span class="x" onmousemove="('comment',' Between the expressions in the various texts cited supra in support of the prescribed two thousand cubits for the Sabbath limit.');">³⁸</span> [the difficulty would arise:] Whence does he [deduce that a Sabbath limit is] two thousand cubits? - He does in fact uphold the word analogy, but<span class="x" onmousemove="('comment',' In reply to the objection from the expression of 'sides' (cf. prev. n.) .');">⁴¹</span> here<span class="x" onmousemove="('comment',' In measuring a Sabbath limit.');">⁴²</span> the case is different<span class="x" onmousemove="('comment',' From other cases where 'side' is used.');">⁴³</span>

Shulchan Arukh, Orach Chayim