Talmud for Yoma 42:1
כלי עץ העשוי לנחת הוא וכל כלי העשוי לנחת אינו מקבל טומאה וחוצץ בפני טומאה אלא מלמד שמגביהין אותו לעולי רגלים ואומרים להם ראו חיבתכם לפני המקום שסילוקו כסדורו שנאמר (שמואל א כא, ז) לשום לחם חום ביום הלקחו
[But surely] it was a wooden vessel, intended for resting, and every wooden vessel intended for resting is not susceptible to uncleanness and sets up a barrier<span class="x" onmousemove="('comment',' . The root 'hazaz' means to cut off, to divide, to serve as an intervening object.');"><sup>1</sup></span> against uncleanness?<span class="x" onmousemove="('comment',' Wooden utensils which are not intended to be moved (as e.g., a table) are not only not susceptible to uncleanness, but they form a barrier against uncleanness, effectively preventing its spread. This is inferred from the passage: And upon whatsoever any of them, when they are dead, doth fall, it shall be unclean; whether it be any vessel of wood, or raiment, or skin, or sack (Lev. XI, 32) . In this passage sack and vessel of wood are cited together, hence our Sages infer that just as a sack is movable and moved, so uncleanness can befall only such wooden vessels as are movable and moved; whereas a wooden vessel meant to rest (or have things placed thereon) is different and hence unsusceptible.');"><sup>2</sup></span>