Parashas Vayakhel · Passuk 35:26
Torah Temimah points to classical source on this unit (verified).
English: Even though this unusual spinning was done for the Mishkan, it does not create liability for Shabbos, because this is not the normal manner of spinning; the exceptional skill does not change that.
Derash applying the distinction between ordinary labor and an exceptional Mishkan technique.
The special Mishkan technique is not treated as the ordinary form of spinning for Shabbos liability.