Reference for Niddah 52:6

וכמה כל שהוא

be no less than four handbreadths high; so R. Meir. But the Sages ruled: This applies only to a big oven but if it is a small one [it is susceptible to uncleanness] ab initio, after its manufacture is completed, whatever its size, and what is left of it [remains unclean] if it was the greater part of it.<span class="x" onmousemove="('comment',' Kel. V, 1. For a fuller explanation cf. Hul. 124a. ');">⁶</span>

Jastrow

Jastrow