The Sages taught: One who enters a Roman bathhouse, where a fire burns beneath the pool of water used for bathing, and where there is the risk of collapse, says:
“May it be Your will, O Lord my God, that you save me from this and similar matters, and do not let ruin or iniquity befall me, and if ruin or iniquity does befall me, let my death be atonement for all of my transgressions.”
Abayye said: One should not say: If ruin befalls me, so as not to open his mouth to Satan and provoke him. As Rabbi Shimon ben Lakish said and as it was taught in a baraita in the name of Rabbi Yosei: One should never open his mouth to Satan by raising, at his own initiative, the possibility of mishap or death.
The Roman bathhouses during the time of the Mishna consisted of several component parts, including a pool of boiling hot water that was under the floor of the bathhouse, which kept the building warm. The collapse of one of the bathhouse walls was liable to cause boiling water or extremely hot air to be released, endangering the lives of those in the bathhouse.
Regarding bloodletting, the Gemara relates:
Rav Aḥa said: One who enters to let blood says: “May it be Your will, O Lord my God, that this enterprise be for healing and that You should heal me. As You are a faithful God of healing and Your healing is truth. Because it is not the way of people to heal, but they have become accustomed.”
Abayye responded and said: One should not say this, as it was taught in the school of Rabbi Yishmael that from the verse, “And shall cause him to be thoroughly healed” (Shmot 21:19), from here we derive that permission is granted to a doctor to heal.
In the time of the Mishna, heretical groups maintained that one is prohibited from interfering in matters that are in God’s purview by engaging in healing. Some explained that a specific Torah source is necessary to permit one to heal illnesses that are not caused by man, as in so doing he acts contrary to God’s will. Others explained that the emphasis of this verse is that doctors are permitted to heal and to accept payment for their services. One might have thought that since he is engaged in the mitzva of saving lives, he may not accept payment. The verse teaches that he may.