Bava Batra — Daf 66a

ואינה מקבלת טומאה במקומה והרודה ממנה בשבת חייב חטאת

וחכמים אומרים אינה כקרקע ואין כותבין עליה פרוזבול ומקבלת טומאה במקומה והרודה ממנה בשבת פטור

התם כדאמר ר' אלעזר טעמא דאמר ר' אלעזר מ"ט דר' אליעזר דכתיב (שמואל א יד, כז) ויטבול אותה ביערת הדבש

מה יער התולש ממנו בשבת חייב חטאת אף דבש הרודה ממנו בשבת חייב חטאת

אלא ר"א דדף דתנן דף של נחתומין שקבעו בכותל ר"א מטהר וחכמים מטמאין

מני אי רבי אליעזר אפילו חקקו ולבסוף קבעו אי רבנן אפילו קבעו ולבסוף חקקו נמי

לעולם רבי אליעזר היא ושאני פשוטי כלי עץ דטומאה דרבנן

מכלל דשאיבה דאורייתא

it is not liable to uncleanness where it is;  and if one takes honey from it on Sabbath, he becomes liable for a sin-offering.  The Sages, however, say that it is not on the same footing as the soil, that it cannot serve as a surety for a prosbul, that it can become unclean where it is, and that one who takes honey from it on Sabbath has not to bring a sin-offering'?  — [It is not this statement either], for there [R. Eliezer's reason is] as reported by R. Eleazar, that we find written in the Scripture, And he dipped it in the honeycomb;  [from which he reasoned that,] just as one who plucks anything from a wood on Sabbath becomes liable for a sin-offering, so one who takes honey from a comb on Sabbath becomes liable for a sin offering.  It must be then the statement of R. Eliezer about the shelf, as we have learnt: 'If a baker's shelf  is fixed in the wall, R. Eliezer says that it is not capable of becoming unclean  and the Sages say that it is.'  [We now ask again], which authority [does the statement adduced above follow]? If it is R. Eliezer, then even if the pipe was first hollowed and then fixed [the water from it should not render the mikweh unfit]:  if it is the Rabbis,  then even if it was first fixed and then hollowed, [it should still spoil the mikweh]?  — It is in truth R. Eliezer, and he makes a difference in the case of flat wooden articles, because their uncleanness was decreed only by the Rabbis.  It would follow from this [would it not], that [the rule about] 'drawn' water derives from the Scripture?