Reference for Shabbat 164:1
היה שלו ושל ע"ז נידון מחצה על מחצה אבניו ועציו ועפריו מטמאים כשרץ שנאמר (דברים ז, כו) שקץ תשקצנו וגו' רבי עקיבא אומר כנדה שנאמר (ישעיהו ל, כב) תזרם כמו דוה מה נדה מטמאה במשא אף ע"ז מטמאה במשא אמר רבה תזרם דאמר קרא נכרינהו מינך כזר צא תאמר לו הכנס אל תאמר לו
If it belongs to him and to the idol, it is judged as half and half.<span class="x" onmousemove="('comment',' E.g., if the wall is two cubits thick, one cubit only is accounted as his portion, and be must retreat another three cubits. ');"><sup>1</sup></span> The stones, timber and earth thereof defile like a [dead] creeping thing [sherez], for it is said, Thou shalt treat a creeping thing.<span class="x" onmousemove="('comment',' Deut. VIII, 26. Shakkez teshakkezenu fr. shekez, something loathsome, which is connected with sherez (E.V.: thou shalt utterly detest it). A sherez defiles by its touch, but not when it is merely carried; but v. discussion infra. ');"><sup>2</sup></span> R. Akiba said: [They defile] like a <i>niddah</i>, because it is said, 'Thou shalt cast them away [tizrem] as a menstruous thing': just as a <i>niddah</i> defiles by carriage, so does an idol defile by carriage. Rabbah observed, Tizrem, mentioned in the verse, means 'thou shalt alienate them from thee as a zar [stranger].' 'Thou shalt say unto it, Get thee hence', but thou shalt not say unto it, Enter hither.<span class="x" onmousemove="('comment',' I.e., one must absolutely reject it (Tosaf. s.v.[H]). ');"><sup>3</sup></span>