Why the Tabernacle Covering Counts as a Tent

"And you shall make the boards for the Tabernacle" (verse 15). The Tabernacle is called "Tabernacle" [mishkan], but the boards are not called "Tabernacle." But if so, "And you shall make a covering for the Tent" (verse 14), is it likewise the case that the covering is not called "Tent" [ohel]? Then what of the question that Rabbi Elazar raised: the hide of an unclean animal, can it convey impurity in the tent of a corpse? Now if the hide of a clean animal does not convey impurity, would the hide of an unclean animal convey impurity? It is different there, for it is written, "And they shall carry the curtains of the Tabernacle, and the Tent of Meeting, its covering, and the covering of tachash" and so on (Numbers 4:25): Scripture compares the upper to the lower; just as the lower is called "Tent," [so too the upper is called "Tent." Nothing that comes from a tree conveys tent-impurity except flax, for the term "Tent"-"Tent" is derived from the Tabernacle: it is written here, "This is the teaching: when a person dies in a tent" (Numbers 19:14), and it is written there, "And he spread the Tent over the Tabernacle" (Exodus 40:19).] If so, just as there the threads were twisted and their thread doubled sixfold, so too here their thread is doubled sixfold. "Tent"-"Tent" is stated to include more.