Commentary for Berakhot 54:4

ומי בדיל והאמר רבי אבין פעם אחת התפלל רבי של שבת בערב שבת ונכנס למרחץ ויצא ושנה לן פרקין ועדיין לא חשכה אמר רבא ההוא דנכנס להזיע וקודם גזירה הוה

But had he made the 'division'? For lo, R. Abin said : On one occasion Rabbi said the Sabbath-Tefillah on the Sabbath-eve, and then entered the bath and came out and taught us our chapter ; and it was not yet dark ! Rab said : He must have gone into the bath-house only to perspire, and that happened before the decree was issued against it.

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot