Bava Batra

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?