Hadith.1873 - Al-Ala narrated from Muhammad ibn Muslim, from Abu Ja'far (as), that he was asked about a man entering the bathhouse while fasting.
Imam (as) said
"There is no harm as long as he does not fear weakness."
Al-Kāfi #417“I once asked abu Ja‘far (a.s.), about a man who uses the bathhouse when fasting. He (the Imam) said, ‘It is not harmful as long as he is...
Maʿānī al-ʾAkhbār #626I asked Ibn Abbas about the faster: Is it permissible for him to perform blood-letting? He said: Yes, as long as he does not fear weakness...